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Nov 15 10 3:30 PM
Huygens found that the atmosphere was hazier than expected because of the presence of dust particles -- called 'aerosols'. Now, scientists are learning how to interpret their analysis of these aerosols, thanks to a special chamber that simulates Titan's atmosphere.When the probe dropped below 40 kilometres in altitude, the haze cleared and the cameras were able to take their first distinct images of the surface. They revealed an extraordinary landscape showing strong evidence that a liquid, possibly methane, has flowed on the surface, causing erosion. Now, images from Cassini are being coupled with the 'ground truth' from Huygens to investigate how conditions on Titan carved out this landscape.As the probe descended, Titan's winds carried it over the surface. A new model of the atmosphere, based on the winds, reveals that Titan's atmosphere is a giant conveyor belt, circulating its gas from the south pole to the north pole and back again.Also, the tentative detection of an extremely low frequency (ELF) radio wave has planetary scientists equally excited. If they confirm that it is a natural phenomenon, it will give them a way to probe into the moon's subsurface, perhaps revealing an underground ocean.Results are presented in the Planetary and Space Science Journal and at a press conference held June 1st in Athens. UK participation in the Cassini-Huygens mission was funded by the Science and technology Facilities Council.Space Fly-by Reveals New Insights Into Titan's LifeScienceDaily (13 Oct. 2008) ‚ÄĒ Cracking the secrets of the atmosphere of Titan, Saturn‚Äôs mysterious moon, and how planetary atmospheres evolve, have come a step closer after evaluation of data from a successful fly-by of its surface by the Cassini spacecraft.Researchers and engineers on the Cassini project, which includes teams from UCL Space and Climate Physics and UCL Mullard Space Science Laboratory (MSSL), were also given a glimpse of how Titan, which has no magnetic field of its own, holds onto remnants of Saturn‚Äôs magnetic field as it caught the big moon on one of its excursions outside Saturn's magnetosphere.Cassini project team member Dr. Nicholas Achilleos, UCL Physics and Astronomy, said: ‚ÄúThe news is significant from two points of view; firstly, from a discovery angle, it is the first time that Titan has ever been found in interplanetary space.‚ÄúNormally it is shielded from the charged particles in the solar wind by Saturn's strong magnetic field. However during the Cassini Titan T32 flyby last year, the solar wind pressure was unusually high which meant that the planet's field could no longer 'hold off' the solar wind flow at the distance of Titan's orbit.‚ÄúAs a result Titan emerged from Saturn‚Äôs very compressed magnetosphere, the shielded region, into the solar wind and interplanetary space.‚ÄĚHe added: ‚ÄúThis data opens up exciting new possibilities and approaches for studying the interaction between planetary magnetic fields and the satellites of those planets.‚ÄĚTitan is the only known moon with a fully developed atmosphere that consists of more than just trace gases, with over 98 per cent of it nitrogen. The encounter showed that Titan‚Äôs atmosphere actually retains a memory of the magnetic field of the plasma that surrounds Saturn and the team believes this memory might last for as long as three hours.Cassini‚Äôs prime mission ended in mid-2008, marking four years since its arrival at Saturn in July 2004. The mission has now been extende extended until 2010 and project members are hopeful of the mission being extended even further.
Nov 15 10 3:32 PM
Nov 15 10 4:01 PM
An ocean seasoned with the chemical ingredients of life may lie hidden beneath the icy surface of Saturn's moon Titan.
The evidence? The entire surface of Titan appears to be sliding around, scientists say, like cheese over tomato sauce on a slice of pizza.
Titan is the largest of the more than 50 known moons orbiting Saturn, and is in fact bigger than the planet Mercury. Titan possesses a thick, planetlike atmosphere ‚ÄĒ the only moon in the solar system known to have a THICK one. (Other moons orbiting Saturn do have light, very veiled atmospheres.) ANOTHER newer REPORT:Cassini Gazes at Veiled Titan
ScienceDaily (Sep. 24, 2010) ‚ÄĒ NASA's Cassini spacecraft will swing high over Saturn's moon Titan on Friday, Sept. 24, taking a long, sustained look at the hazy moon. At closest approach, Cassini will fly within 8,175 kilometers (5,080 miles) above the hazy moon's surface. This flyby is the first in a series of high-altitude Titan flybys for Cassini over the next year and a half.
Cassini's composite infrared spectrometer instrument will be probing Titan's stratosphere to learn more about its vertical structure as the seasons change. Equinox, when the sun shone directly over the equator, occurred in August 2009, and the northern hemisphere is now in spring.
Another instrument, the visual and infrared mapping spectrometer, will be mapping an equatorial region known as Belet at a resolution of 5 kilometers (3 miles) per pixel. This mosaic will complement the mosaics that were obtained in earlier Titan flybys in January and April. This spectrometer will also look for clouds at northern mid-latitudes and near the poles.
Cassin's visible-light imaging cameras will also be taking images of Titan's trailing hemisphere, or the side that faces backward as Titan orbits around Saturn. If Titan cooperates and has a cloudy day, scientists plan to analyze the images for cloud patterns.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C.
Scientists had long suspected that an underground ocean might exist on Titan, much like the ones thought to exist on Jupiter's moons Ganymede, Callisto and Europa.
"Models of heat flow in Titan's interior suggested years ago that Titan would likely have an internal water or water-ammonia ocean," said Ralph Lorenz, a Cassini radar team member at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
Lorenz and his colleagues analyzed several years' worth of radar data from the Cassini-Huygens mission. They found evidence that some features on the moon's surface had drifted.
"As we were mapping Titan's surface, we were building maps up in little strips. Some of these strips overlapped, help tying the map together, but when you looked at where the features were in one strip compared with another strip, the coordinates weren't the same," Lorenz explained. life on Titan. There is a growing sense that Titan may have all the ingredients for life: thermodynamic disequilibrium, abundant carbon-containing molecules and a fluid environment.
And there is also evidence that liquid water may not be as important as everybody has assumed. Schulze-Makuch and co point to recent evidence that some microorganisms can make there own water by chewing on various hydrocarbons.
Nov 15 10 4:20 PM
Nov 15 10 4:24 PM
Dec 2 10 6:27 AM
ScienceDaily (17 Jan. 2007) ‚ÄĒ Two years ago, planetary scientists across the world watched as Europe and the US did something amazing. The Huygens descent module drifted down through the hazy atmosphere of Saturn's moon Titan, beaming its data back to Earth via the Cassini mothership. Today, Huygens's data are still continuing to surprise researchers.
Titan holds a unique place in the Solar System. It is the only moon covered in a significant atmosphere. The atmosphere has long intrigued scientists as it may be similar to that of the early Earth but the deeper mystery was: what lies beneath the haze?
The European Space Agency built the Huygens spacecraft to find out. The probe, carrying scientific investigations involving both sides of the Atlantic, hitched a ride on NASA's Cassini spacecraft. Together Cassini and Huygens make an unprecedented joint space mission - as a major milestone, Huygens parachuted to the surface of Titan on 14 January 2005.
While Cassini keeps flying by this moon of Saturn collecting new amazing data, one can say that the data collected by Huygens‚Äôs six instruments during its 2.5-hour descent and touch-down have provided the most spectacular view of this world yet and first dramatic change in the way we now think about it.
"When you put all the data together, we get a very rich picture of Titan," says Ath√©na Coustenis, Observatoire de Paris, France, "The Descent Imager/Spectral Radiometer (DISR) pictures were an enormous surprise. We had expected a much smoother landscape." Instead, they saw a varied landscape of channels that had been formed by some kind of flowing liquid.
"At the landing site we also saw rounded ice pebbles," says Jonathan Lunine, University of Arizona. The Surface Science Package (SSP) provided the final piece in this particular puzzle. The impact it detected when Huygens touched down indicated that the spacecraft had come to rest in compacted gravel. "Put it all together and it is clear that Huygens landed in an outflow wash," says Lunine.
The Gas Chromatograph and Mass Spectrometer (GCMS) instrument confirmed the nature of the liquid that shapes the surface of Titan. It detected methane evaporating from the Huygens landing site. "Methane on Titan plays the role that water plays on Earth," concludes Lunine. But there are still mysteries. It is not yet clear whether the methane falls mostly as a steady drizzle or as an occasional deluge.
The GCMS also detected two isotopes of argon. Both have important stories to tell. The Ar40 indicates that the interior of Titan is still active. This is unusual in a moon and indicates that perhaps an insulating layer of water ice and methane is buried in the moon itself, close to the surface, trapping the heat inside it. Occasionally, this heat causes the so-called cryo-volcanoes to erupt. Icy 'lava' flows from these cryo-volcanoes have been seen from the orbiting Cassini spacecraft. Because Ar40 is so heavy, it is mostly concentrated towards the base of the atmosphere, so having Huygens on the surface was essential for its detection.
Daniel Gautier, Observatoire de Paris, France, thinks that the other isotope, Ar36, is telling scientists that Titan formed after Saturn, at a time when the primeval gas cloud that became the Solar System had cooled to about 40 ¬ļK (-233 ¬ļC).
The atmosphere of Titan held surprises too. "Huygens made a fantastic and unexpected discovery about the wind," says Gautier. At an altitude of around 60 kilometres, the wind speed dropped, essentially to zero. Explaining this behaviour presents a challenge for theoreticians who are developing computer models of the moon‚Äôs atmospheric circulationThe Huygens Atmosphere Structure Instrument (HASI) provided the temperature of the atmosphere from 1600 kilometres altitude down to the surface. "This has helped put all the other data into context," says Coustenis. Huygens measured the composition profile of the atmosphere to be a mixture of nitrogen, methane and ethane. The methane and ethane provide humidity, as water does in Earth‚Äôs atmosphere. At the surface of Titan, Huygens measured the temperature to be 94 ¬ļK (-179 ¬ļC) with a humidity of 45 percent. Even though the Huygens data set is now two years old, the discoveries have not yet stopped. "There are lots of surprises still to come from this data," says Francesca Ferri, Universit√† degli Studi di Padova. In addition, Huygens gives planetary scientists a wealth of 'ground-truth' to complement and help interpret the observations still coming from Cassini. At the beginning of 2007, Cassini showed that liquid methane is present on Titan in lakes.Cassini, whose experiments also see a joint US and European participation, will make another 22 fly-bys of Titan - the first on 13 January - between now and the end of its scheduled mission in the summer of 2008. The Cassini-Huygens scientists are discussing their options to extend the mission. One idea, says Christophe Sotin, Universit√© de Nantes, France, would be to use Cassini to study the newly discovered lakes. Huygens has exceeded expectations and shown Titan to be an 'alien earth', giving planetary scientists a new world of fascination to explore.
ScienceDaily (29 Jan. 2010) During T-66, the Imaging Science Subsystem is set to acquire high-resolution observations during and after closest-approach, covering territory from the trailing hemisphere at high southern latitudes northeast to near-equatorial Adiri. On the inbound leg, the Visual and Infrared Mapping Spectrometer will have the opportunity to do one stellar occultation. (A stellar occultation occurs when an intervening body -- in this case Titan -- blocks the light from a star). Thursday's stellar occultation should allow the Cassini science team to further constrain the composition and the spectral properties of Titan's atmosphere.Although this latest flyby is dubbed "T66," planning changes early in the orbital tour made this the 67th targeted flyby of Titan. T66 is the 22nd Titan encounter in Cassini's Solstice Mission.The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter. The Huygens probe, built and managed by the European Space Agency, was bolted to Cassini and rode along during its nearly seven-year journey to Saturn, before being released for its descent through Titan's atmosphere.
ScienceDaily (Oct. 4, 2010)
ScienceDaily (14March 2007) ‚ÄĒ Instruments on NASA's Cassini spacecraft have found evidence for seas, likely filled with liquid methane or ethane, in the high northern latitudes of Saturn's moon Titan. One such feature is larger than any of the Great Lakes of North America and is about the same size as several seas on Earth.Cassini's radar instrument imaged several very dark features near Titan's north pole. Much larger than similar features seen before on Titan, the largest dark feature measures at least 100,000 square kilometers (39,000 square miles). Since the radar has caught only a portion of each of these features, only their minimum size is known. Titan is the second largest moon in the solar system and is about 50 percent larger than Earth's moon. "We've long hypothesized about oceans on Titan and now with multiple instruments we have a first indication of seas that dwarf the lakes seen previously," said Dr. Jonathan Lunine, Cassini interdisciplinary scientist at the University of Arizona, Tucson. While there is no definitive proof yet that these seas contain liquid, their shape, their dark appearance in radar that indicates smoothness, and their other properties point to the presence of liquids. The liquids are probably a combination of methane and ethane, given the conditions on Titan and the abundance of methane and ethane gases and clouds in Titan's atmosphere. Cassini's visual and infrared mapping spectrometer also captured a view of the region, and the team is working to determine the composition of the material contained within these features to test the hypothesis that they are liquid-filled.Cassini scientists had been looking for the glint, also known as a specular reflection, since the spacecraft began orbiting Saturn in 2004. But Titan's northern hemisphere, which has more lakes than the southern hemisphere, has been veiled in winter darkness.The sun only began to directly illuminate the northern lakes recently as it approached the equinox of August 2009, the start of spring in the northern hemisphere. Titan's hazy atmosphere also blocked out reflections of sunlight in most wavelengths. This serendipitous image was captured on July 8, 2009, using Cassini's visual and infrared mapping spectrometer.The image will be presented Friday, Dec. 18, at the fall meeting of the American Geophysical Union in San Francisco."This one image communicates so much about Titan -- thick atmosphere, surface lakes and an otherworldliness," said Bob Pappalardo, Cassini project scientist, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It's an unsettling combination of strangeness yet similarity to Earth. This picture is one of Cassini's iconic images."Titan, Saturn's largest moon, has captivated scientists because of its many similarities to Earth. Scientists have theorized for 20 years that Titan's cold surface hosts seas or lakes of liquid hydrocarbons, making it the only other planetary body besides Earth believed to harbor liquid on its surface. While data from Cassini have not indicated any vast seas, they have revealed large lakes near Titan's north and south poles.In 2008, Cassini scientists using infrared data confirmed the presence of liquid in Ontario Lacus, the largest lake in Titan's southern hemisphere. But they were still looking for the smoking gun to confirm liquid in the northern hemisphere, where lakes are also larger.Katrin Stephan, of the German Aerospace Center (DLR) in Berlin, an associate member of the Cassini visual and infrared mapping spectrometer team, was processing the initial image and was the first to see the glint on July 10th."I was instantly excited because the glint reminded me of an image of our own planet taken from orbit around Earth, showing a reflection of sunlight on an ocean," Stephan said. "But we also had to do more work to make sure the glint we were seeing wasn't lightning or an erupting volcano."Team members at the University of Arizona, Tucson, processed the image further, and scientists were able to compare the new image to radar and near-infrared-light images acquired from 2006 to 2008.They were able to correlate the reflection to the southern shoreline of a lake called Kraken Mare. The sprawling Kraken Mare covers about 400,000 square kilometers (150,000 square miles), an area larger than the Caspian Sea, the largest lake on Earth. It is located around 71 degrees north latitude and 337 degrees west latitude.The finding shows that the shoreline of Kraken Mare has been stable over the last three years and that Titan has an ongoing hydrological cycle that brings liquids to the surface, said Ralf Jaumann, a visual and infrared mapping spectrometer team member who leads the scientists at the DLR who work on Cassini. Of course, in this case, the liquid in the hydrological cycle is methane rather than water, as it is on Earth."These results remind us how unique Titan is in the solar system," Jaumann said. "But they also show us that liquid has a universal power to shape geological surfaces in the same way, no matter what the liquid is."The new infrared image is available online at: http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://wwwvims.lpl.arizona.edu.
Glint of Sunlight Confirms Liquid in Lake on Saturn's Moon Titan
ScienceDaily (18 Dec. 2009) ‚ÄĒ NASA's Cassini Spacecraft has captured the first flash of sunlight reflected off a lake on Saturn's moon Titan, confirming the presence of liquid on the part of the moon dotted with many large, lake-shaped basins.OLDER REPORT:
http://www.nasa.gov/multimedia/videogallery/index.html?collection_id=14658&media_id=16290407Posted:07/19/2010The Usual Suspects: Titan Lake Clues(03:04)Posted:07/14/2010See Beautiful Ontario Lacus(01:22)Posted:07/14/2010Titan Canyon Country(01:18)Posted:03/04/
ScienceDaily (Feb. 21, 2008) ‚ÄĒ Saturn's orange moon Titan has hundreds of times more liquid hydrocarbons than all the known oil and natural gas reserves on Earth, according to new data from NASA's Cassini spacecraft. The hydrocarbons rain from the sky, collecting in vast deposits that form lakes and dunesAn artist's imagination of hydrocarbon pools, icy and rocky terrain on the surface of Saturn's largest moon Titan. (Credit: Steven Hobbs (Brisbane, Queensland, Australia).)
The new findings from the study led by Ralph Lorenz, Cassini radar team member from the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., are reported in the Jan. 29 issue of the Geophysical Research Letters"Titan is just covered in carbon-bearing material -- it's a giant factory of organic chemicals," said Lorenz. "This vast carbon inventory is an important window into the geology and climate history of Titan."At a balmy minus 179 degrees Celsius (minus 290 degrees Fahrenheit), Titan is a far cry from Earth. Instead of water, liquid hydrocarbons in the form of methane and ethane are present on the moon's surface, and tholins probably make up its dunes. The term "tholins"was coined by Carl Sagan in 1979 to describe the complex organic molecules at the heart of prebiotic chemistry.Cassini has mapped about 20 percent of Titan's surface with radar. Several hundred lakes and seas have been observed, with each of several dozen estimated to contain more hydrocarbon liquid than Earth's oil and gas reserves. The dark dunes that run along the equator contain a volume of organics several hundred times larger than Earth's coal reserves.Proven reserves of natural gas on Earth total 130 billion tons, enough to provide 300 times the amount of energy the entire United States uses annually for residential heating, cooling and lighting. Dozens of Titan's lakes individually have the equivalent of at least this much energy in the form of methane and ethane."This global estimate is based mostly on views of the lakes in the northern polar regions. We have assumed the south might be similar, but we really don't yet know how much liquid is there," said Lorenz. Cassini's radar has observed the south polar region only once, and only two small lakes were visible. Future observations of that area are planned during Cassini's proposed extended mission.Scientists estimated Titan's lake depth by making some general assumptions based on lakes on Earth. They took the average area and depth of lakes on Earth, taking into account the nearby surroundings, like mountains. On Earth, the lake depth is often 10 times less than the height of nearby terrain."We also know that some lakes are more than 10 meters or so deep because they appear literally pitch-black to the radar. If they were shallow we'd see the bottom, and we don't," said Lorenz.The question of how much liquid is on the surface is an important one because methane is a strong greenhouse gas on Titan as well as on Earth, but there is much more of it on Titan. If all the observed liquid on Titan is methane, it would only last a few million years, because as methane escapes into Titan's atmosphere, it breaks down and escapes into space. If the methane were to run out, Titan could become much colder. Scientists believe that methane might be supplied to the atmosphere by venting from the interior in cryovolcanic eruptions. If so, the amount of methane, and the temperature on Titan, may have fluctuated dramatically in Titan's past."We are carbon-based life, and understanding how far along the chain of complexity towards life that chemistry can go in an environment like Titan will be important in understanding the origins of life throughout the universe," added Lorenz.Cassini's next radar flyby of Titan is on Feb. 22, when the radar instrument will observe the Huygens probe landing site.
ScienceDaily (04 March2009) ‚ÄĒ Titan's vast dune fields, which may act like weather vanes to determine general wind direction on Saturn's biggest moon, have been mapped by scientists who compiled four years of radar data collected by the Cassini spacecraft.
Titan's rippled dunes are generally oriented east-west. Surprisingly, their orientation and characteristics indicate that near the surface, Titan's winds blow toward the east instead of toward the west. This means that Titan's surface winds blow opposite the direction suggested by previous global circulation models of Titan."At Titan there are very few clouds, so determining which way the wind blows is not an easy thing, but by tracking the direction in which Titan's sand dunes form, we get some insight into the global wind pattern," says Ralph Lorenz, Cassini radar scientist at Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "Think of the dunes sort of like a weather vane, pointing us to the direction the winds are blowing." A paper based on these findings appeared in the Feb. 11 issue of Geophysical Research Letters."Titan's dunes are young, dynamic features that interact with topographic obstacles and give us clues about the wind regimes," said Jani Radebaugh, Brigham Young University, Provo, Utah. "Winds come at these dunes from at least a couple of different directions, but then combine to create the overall dune orientation."The new map, based on all the high-resolution radar data collected during a four-year period, is now available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .The wind pattern is important for planning future Titan explorations that might involve balloon-borne experiments.Some 16,000 dune segments were mapped out from about 20 radar images, digitized and combined to produce the new map.Titan's dunes are believed to be made up of hydrocarbon sand grains likely derived from organic chemicals in Titan's smoggy skies. The dunes wrap around high terrain, which provides some idea of their height. They accumulate near the equator, and may pile up there because drier conditions allow for easy transport of the particles by the wind. Titan's higher latitudes contain lakes and may be "wetter" with more liquid hydrocarbons, not ideal conditions for creating dunes.Cassini, which launched in 1997 and is now in extended mission operations, continues to blaze its trail around the Saturn system and will visit Titan again on March 27. Seventeen Titan flybys are planned this year.The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.
ScienceDaily (Sep. 29, 2009) ‚ÄĒ A team of international scientists led by Mirjam Langhans, from the German Aerospace Center (DLR), will present first results of a global analysis of spatial patterns, occurrence and origin of river channels on Titan at the European Planetary Science Congress in Potsdam, Germany, on Wednesday 16 September.
To date scientists have focused their investigations on single channels due to the fact that radar and spectral data have only been captured for some narrow areas of the surface below the thick nitrogen atmosphere of this mysterious moon of Saturn. This data jigsaw puzzle is increasingly being filled in through further fly bys of Titan by NASA‚Äôs Cassini spacecraft. Now, for the first time, the DLR team has developed a global perspective of the deposits of liquid hydrocarbons, such as methane and ethane, and their effected forms of erosion.Beside the Earth, Titan is the only body in the Solar System where liquids directly have been proved to exist. The moon‚Äôs exceptionally thick atmosphere, where chemical reactions occur at freezing temperatures of -179 degrees Celsius, makes this second largest moon of the Solar System of special interest for planetary science.The DLR scientists have compiled a global map of Titan, which combines all radar data and details the surface of Titan down to 300 meters in size. Furthermore, data in near infrared wavelengths have been captured for a wide band around the equator by Cassini‚Äôs Visual and Infrared Mapping Spectrometer (VIMS) with a resolution of up to 300 meters per pixel.On this equatorial band, bright continent areas and extensive dune regions can be distinguished. Dark spots on the continent areas are of special interest, because they are supposed to be fluvial deposits. Additional radar data show channels precisely linked to them, which are dry, canyon-like, and broadly distributed.Towards the north pole, the picture is much richer. There is a dense network of branching, active river systems similar to those on Earth. They are visible down to small tributaries on radar images and can be seen flowing into multiple lakes. Contrastingly, hardly any channels are found at the south pole.‚ÄúThe observations of the extensive river structures at the north pole have led the team to a fascinating conclusion: there must be heavy and frequent rain of liquid hydrocarbons. Furthermore the measured channels provide first clues about the composition and relative age of different regions of Titan,‚ÄĚ said Langhans.
Dec 2 10 6:35 AM
Dec 15 10 12:10 AM
ScienceDaily (14 Dec. 2010) ‚ÄĒ NASA's Cassini spacecraft has found possible ice volcanoes on Saturn's moon Titan that are similar in shape to those on Earth that spew molten rock.OLDER REPORT:Cassini Flies By Saturn's Moon Titan, Sees More CratersScienceDaily (04 May 2006) ‚ÄĒ Saturn's moon Titan continued to surprise scientists during a flyby that took Cassini into regions previously unexplored by radar. Two very noticeable circular features, possible impact craters or calderas, appear in the latest radar images taken during the flyby on 30 April 2006. The flyby targeted Xanadu, one of the most prominent features on Titan, visible even from telescopes on Earth. The origin of Xanadu is still unknown, but the radar images reveal details previously unseen, such as numerous curvy features that may indicate fluid flows. Scientists speculate that two prominent circular features are probably impact craters but they don't rule out the possibility that they might be calderas or volcanoes. Sand dunes, discovered in previous flybys, continue to crisscross Titan's surface. Communication from the spacecraft was temporarily interrupted for nearly five hours during the data playback following the flyby. The most important science data from the flyby were protected by a contingency plan put in place in advance of the flyby. The flight team believes the outage was likely due to a galactic cosmic-ray hit on a power switch in the spacecraft communications subsystem. The anomaly resulted in the loss of some science data. However, the spacecraft is now performing normally. This was the 14th Titan flyby for Cassini, with nine more remaining this year. The next will be May 20, 2006. During the nominal four-year mission Cassini will perform 45 Titan flybys. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech, manages the mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL.
Topography and surface composition data have enabled scientists to make the best case yet in the outer solar system for an Earth-like volcano landform that erupts in ice. The results were presented at the American Geophysical Union meeting in San Francisco.
"When we look at our new 3-D map of Sotra Facula on Titan, we are struck by its resemblance to volcanoes like Mt. Etna in Italy, Laki in Iceland and even some small volcanic cones and flows near my hometown of Flagstaff," said Randolph Kirk, who led the 3-D mapping work, and is a Cassini radar team member and geophysicist at the U.S. Geological Survey (USGS) Astrogeology Science Center in Flagstaff, Ariz.
Scientists have been debating for years whether ice volcanoes, also called cryovolcanoes, exist on ice-rich moons, and if they do, what their characteristics are. The working definition assumes some kind of subterranean geological activity warms the cold environment enough to melt part of the satellite's interior and sends slushy ice or other materials through an opening in the surface. Volcanoes on Jupiter's moon Io and Earth spew silicate lava.
Some cryovolcanoes bear little resemblance to terrestrial volcanoes, such as the tiger stripes at Saturn's moon Enceladus, where long fissures spray jets of water and icy particles that leave little trace on the surface. At other sites, eruption of denser materials might build up volcanic peaks or finger-like flows. But when such flows were spotted on Titan in the past, theories explained them as non-volcanic processes, such as rivers depositing sediment. At Sotra, however, cryovolcanism is the best explanation for two peaks more than 3000 feet high with deep volcanic craters and finger-like flows.
"This is the very best evidence, by far, for volcanic topography anywhere documented on an icy satellite," said Jeffrey Kargel, a planetary scientist at the University of Arizona, Tucson. "It's possible the mountains are tectonic in origin, but the interpretation of cryovolcano is a much simpler, more consistent explanation."
Kirk and colleagues analyzed new Cassini radar images. His USGS group created the topographic map and 3-D flyover images of Sotra Facula. Data from Cassini's visual and infrared mapping spectrometer revealed the lobed flows had a composition different from the surrounding surface. Scientists have no evidence of current activity at Sotra, but they plan to monitor the area.
"Cryovolcanoes help explain the geological forces sculpting some of these exotic places in our solar system," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "At Titan, for instance, they explain how methane can be continually replenished in the atmosphere when the sun is constantly breaking that molecule down."OLDER REPORT:
ScienceDaily (Mar. 2, 2006) ‚ÄĒ Data from ESA's Huygens probe have been used to validate a new model of the evolution of Titan, Saturn‚Äôs largest moon, showing that its methane supply may be locked away in a kind of methane-rich ice.
The presence of methane in Titan's atmosphere is one of the major enigmas that the NASA/ESA/ASI Cassini-Huygens mission is trying to solve.
Titan was revealed last year to have spectacular landscapes apparently carved by liquids. The Cassini-Huygens mission also showed that there is not after all a lot of liquid methane remaining on the moon‚Äôs surface, and so it is not clear where the atmospheric methane gas comes from.
Using the Cassini-Huygens findings, a model of Titan's evolution, focusing on the source of Titan‚Äôs atmospheric methane, has been developed in a joint study by the University of Nantes, France, and the University of Arizona in Tucson, USA.
"This model is in agreement with the observations made so far by both the Huygens probe that landed on Titan on 14 January 2005 and the remote sensing instruments on board the Cassini spacecraft," said Gabriel Tobie, of the Laboratoire de Planetologie et Geodynamique de Nantes, and lead author of an article in Nature.
There is a difference between volcanism on Earth and ‚Äėcryovolcanism‚Äô on Titan. Volcanoes on Titan would involve ice melting and ice degassing, which is analogous to silicate volcanism on Earth, but with different materials.
Methane, playing a role on Titan similar to water on Earth, would have been released during three episodes: a first one following the accretion and differentiation period, a second episode about 2000 million years ago when convection started in the silicate core and a geologically recent one (last 500 million years ago) due to enhanced cooling of the moon by solid-state convection in the outer crust.
This means that Titan‚Äôs methane supply may be stored in a kind of methane-rich ice. The scientists suggest that the ice, called a ‚Äėclathrate hydrate‚Äô, forms a crust above an ocean of liquid water mixed with ammonia.
"As methane is broken down by light-induced chemical reactions over a timescale of tens of millions of years, it can‚Äôt just be a remnant of the atmosphere present when Titan itself was formed, and it must be replenished quite regularly," said Tobie.
"According to our model, during the last outgassing episode, the dissociation of the methane clathrate and hence release of methane are induced by thermal anomalies within the icy crust, which are generated by crystallisation in the internal ocean," said Tobie.
"As this crystallisation started only relatively recently (500 to 1000 million years ago), we expect that the ammonia-water ocean is still present few tens of kilometres below the surface and that methane outgassing is still operating. Even though the outgassing rate is expected to decline now (it peaked about 500 million years ago), release of methane through cryovolcanic eruptions should still occur on Titan," explained Tobie.
"Parts of the clathrate crust might be warmed from time to time by ‚Äėcryovolcanic‚Äô activity on the moon, causing it to release its methane into the atmosphere. These outbursts could produce temporary flows of liquid methane on the surface, accounting for the river-like features seen on Titan‚Äôs surface.
"Cassini‚Äôs instruments, in particular its Visible and Infrared Mapping Spectrometer (VIMS), should detect an increasing number of cryovolcanic features and, if we are lucky, may eventually detect eruptions of methane," added Tobie.
If they are right, say the researchers, then Cassini and future missions to Titan should also be able to detect the existence of their possible subsurface liquid water-ammonia ocean.
Later in the mission, Cassini itself will make measurements that will confirm (or not) the presence of the internal water ocean, and also the existence of a rocky core.
ScienceDaily (29 Mar. 2009) ‚ÄĒ "Fly me to the moon"-to Saturn's moon Titan, that is. New Titan movies and images are providing a bird's-eye view of the moon's Earth-like landscapes.The new flyover maps show, for the first time, the 3-D topography and height of the 1,200-meter (4,000-foot) mountain tops, the north polar lake country, the vast dunes more than 100 meters (300 feet) high that crisscross the moon, and the thick flows that may have oozed from possible ice volcanoes.The topographic maps were made from stereo pairs of radar images. They are available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .Cassini radar team member Randy Kirk with the Astrogeology Science Center at the U.S. Geological Survey in Flagstaff, Ariz., created the maps. He used some of the 20 or so areas where two or more overlapping radar measurements were obtained during 19 Titan flybys. These stereo overlaps cover close to two percent of Titan's surface. The process of making topographic maps from them is just beginning, but the results already reveal some of the diversity of Titan's geologic features."These flyovers let you take in the bird's-eye sweeping views of Titan, the next best thing to being there," said Kirk. "We've mapped many kinds of features, and some of them remind me of Earth. Big seas, small lakes, rivers, dry river channels, mountains and sand dunes with hills poking out of them, lava flows."Kirk will present these results today at the Lunar and Planetary Science Conference in The Woodlands, Texas.High and low features are shown in unprecedented detail at about 2.4-kilometer (1.5-mile) resolution. The maps show some features that may be volcanic flows. These flows meander across a shallow basin in the mountains. One area suspected to be an ice volcano, Ganesa Macula, does not appear to be a volcanic dome. It may still have originated as a volcano, but it's too soon to know for sure. "It could be a volcanic feature, a crater, or something else that has just been heavily eroded," added Kirk.The stereo coverage includes a large portion of Titan's north polar lakes of liquid ethane and methane. Based on these topographical models, scientists are better able to determine the depth of lakes. The highest areas surrounding the lakes are some 1,200 meters (about 4,000 feet) above the shoreline. By comparing terrain around Earth to the Titan lakes, scientists estimate their depth is likely about 100 meters (300 feet) or less.More 3-D mapping of these lakes will help refine these depth estimates and determine the volume of liquid hydrocarbons that exist on Titan. This information is important because these liquids evaporate and create Titan's atmosphere. Understanding this methane cycle can provide clues to Titan's weather and climate.Launched in 1997, Cassini completed its primary four-year mission in 2008 and is now in extended mission operations, which run through September 2010. Over the course of the mission, Cassini plans to map more than three percent of Titan's surface in 3-D. About 38 percent of Titan's surface has been mapped with radar so far. On March 27, Cassini will complete its 52nd targeted flyby of Titan.The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.
Cassini launched Oct. 15, 1997, and began orbiting Saturn in 2004. Saturn has more than 60 known moons, with Titan being the largest. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency (ASI). JPL manages the mission for NASA's Science Mission Directorate at the agency's Headquarters in Washington.The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and ASI, working with team members from the U.S. and several European countries. The visual and infrared mapping spectrometer was built by JPL, with a major contribution by ASI. The visual and infrared mapping spectrometer science team is based at the University of Arizona, Tucson.
For more information about the Cassini mission, visit: http://www.nasa.gov/cassini
ScienceDaily (26 Jan. 2010) ‚ÄĒ Hills with a wrinkly radial pattern stand out in a new radar image of Saturn's moon Titan captured by NASA's Cassini spacecraft on 28 Dec. 2009.The grooved mounds in the picture, which are located in a northern hemisphere region known as Belet, are about 80 kilometers (50 miles) wide and about 60 meters (200 feet) high.The shapes of these landscape features have not been seen on Titan before, though they bear similarity to spidery features known as coronae on Venus. A corona is a circular to elliptical feature thought to result from the flow of heat in a planet's interior.Like forensic scientists, radar team members are trying to sleuth out what created these lines and hills on Titan."This star-shaped pattern of the hills indicates something significant happening in the middle of the star," said Steve Wall of NASA's Jet Propulsion Laboratory, Pasadena, Calif., a Cassini scientist on the radar team. "It might be caused by tectonic forces, such as the forces that pull the crust of a planet apart, or rainfall that leads to erosion, or an ice intrusion like a dike."All of these forces produce grooves on Earth's surface, but Wall says the radar team is not yet sure what is happening on Titan.
ScienceDaily (17 Aug.2010) ‚ÄĒ Saturn's moon Titan ripples with mountains, and scientists have been trying to figure out how they form. The best explanation, it turns out, is that Titan is shrinking as it cools, wrinkling up the moon's surface like a raisin.
A new model developed by scientists working with radar data obtained by NASA's Cassini spacecraft shows that differing densities in the outermost layers of Titan can account for the unusual surface behavior. Titan is slowly cooling because it is releasing heat from its original formation and radioactive isotopes are decaying in the interior. As this happens, parts of Titan's subsurface ocean freeze over, the outermost ice crust thickens and folds, and the moon shrivels up. The model is described in an article now online in the Journal of Geophysical Research.
"Titan is the only icy body we know of in the solar system that behaves like this," said Giuseppe Mitri, the lead author of the paper and a Cassini radar associate based at the California Institute of Technology in Pasadena. "But it gives us insight into how our solar system came to be."
An example of this kind of process can also be found on Earth, where the crumpling of the outermost layer of the surface, known as the lithosphere, created the Zagros Mountains in Iran, Mitri said.
Titan's highest peaks rise up to about two kilometers (6,600 feet), comparable to the tallest summits in the Appalachian Mountains. Cassini was the first to spot Titan's mountains in radar images in 2005. Several mountain chains on Titan exist near the equator and are generally oriented west-east. The concentration of these ranges near the equator suggests a common history.
While several other icy moons in the outer solar system have peaks that reach heights similar to Titan's mountain chains, their topography comes from extensional tectonics -- forces stretching the ice shell -- or other geological processes. Until now, scientists had little evidence of contractional tectonics -- forces shortening and thickening the ice shell. Titan is the only icy satellite where the shortening and thickening are dominant.
Mitri and colleagues fed data from Cassini's radar instrument into computer models of Titan developed to describe the moon's tectonic processes and to study the interior structure and evolution of icy satellites. They also made the assumption that the moon's interior was only partially separated into a mixture of rock and ice, as suggested by data from Cassini's radio science team.
Scientists tweaked the model until they were able to build mountains on the surface similar to those Cassini had seen. They found the conditions were met when they assumed the deep interior was surrounded by a very dense layer of high-pressure water ice, then a subsurface liquid-water-and-ammonia ocean and an outer water-ice shell. So the model, Mitri explained, also supports the existence of a subsurface ocean.
Each successive layer of Titan's interior is colder than the one just inside it, with the outermost surface averaging a chilly 94 Kelvin (minus 290 degrees Fahrenheit). So cooling of the moon causes a partial freezing of the subsurface liquid ocean and thickening of the outer water ice shell. It also thickens the high-pressure ice. Because the ice on the crust is less dense than the liquid ocean and the liquid ocean is less dense than the high-pressure ice, the cooling means the interior layers lose volume and the top "skin" of ice puckers and folds.
Since the formation of Titan, which scientists believe occurred around four billion years ago, the moon's interior has cooled significantly. But the moon is still releasing hundreds of gigawatts of power, some of which may be available for geologic activity. The result, according to the model, was a shortening of the radius of the moon by about seven kilometers (four miles) and a decrease in volume of about one percent.
"These results suggest that Titan's geologic history has been different from that of its Jovian cousins, thanks, perhaps, to an interior ocean of water and ammonia," said Jonathan Lunine, a Cassini interdisciplinary scientist for Titan and co-author on the new paper. Lunine is currently based at the University of Rome, Tor Vergata, Italy. "As Cassini continues to map Titan, we will learn more about the extent and height of mountains across its diverse surface."
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries. JPL is a division of the California Institute of Technology in Pasadena.
More Cassini information is available, at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.
ScienceDaily (21 Dec. 2007) ‚ÄĒ By analyzing images from NASA‚Äôs Cassini Radar instrument, a Brigham Young University professor helped discover and analyze mountains on Saturn‚Äôs largest moon, additional evidence that it has some of the most earthlike processes of any celestial body in the solar system.
According to the study, Titan‚Äôs mountains are most likely made of water ice and are relatively small in height, at most 2 km (1.25 mi) from base to peak. The consistently short height of Titan‚Äôs mountains provides evidence that they have been subject to similar amounts of erosion, that they are roughly the same age or that the materials are behaving in a way that prevents them from growing taller.
Planetary scientist Jani Radebaugh is lead author of the discovery paper in the December issue of the astronomy journal Icarus. The images retrieved by the Cassini Radar are the first images showing the details of Titan‚Äôs surface ‚Äď previous spacecraft and telescopes could not pierce the haze and clouds surrounding the moon to the surface.
The discovery of mountains on Titan grew out of Radebaugh‚Äôs collaboration with a research team that recently found sand dunes and methane lakes on Titan. Radebaugh was a coauthor on the Science study that introduced Titan‚Äôs sand dunes in May 2006 as well as the Nature study that introduced Titan‚Äôs methane lakes in January 2007.
‚ÄúSince this is the first time humans have been able to see through the haze to Titan‚Äôs surface, it was shocking to find these mountains, channels, dunes, and cryo-lava flows,‚ÄĚ Radebaugh said. ‚ÄúWe had to wait until we got all the way to Titan to see these landforms that are so similar to Earth.‚ÄĚ
Upon receiving the images from NASA, Radebaugh, in collaboration with the Cassini Radar Team, discovered the mountains and began analyzing their characteristics. With no instrument to precisely measure the mountains‚Äô height, Radebaugh looked at the light and shadows in the radar images to calculate the mountains‚Äô slope and then derive their height.
‚ÄúDr. Radebaugh‚Äôs work represents an important advance in our understanding of that icy moon and the Earth,‚ÄĚ said Dr. Jason Barnes, a research scientist at the NASA Ames Research Center. ‚ÄúHer discovery tells us about the mountain-building process in general and about Titan‚Äôs crust in particular.‚ÄĚ
Prior to Cassini, scientists assumed that most of the topography on Titan would be impact structures, yet these new findings reveal that similar to Earth, the mountains were formed through geological processes on the moon.
Radebaugh proposes four possible explanations for the formation of the mountains on Titan. The first possibility is that the mountains were thrust up from crustal compression, horizontal forces smashing the crust together and upward. Alternatively, Titan‚Äôs mountains may have formed through spreading or separation of the crust, in the same way that Utah‚Äôs Wasatch Mountains separated from the Oquirrh Mountains to the west.
It‚Äôs also possible some of the mountains have been created by impact craters that threw out blocks of material, or that erosion stripped away a preexisting layer of material and left high-standing features like the mountains.
Since the processes on Titan are so similar to Earth‚Äôs, Radebaugh also concluded in the study that Titan may be an interesting laboratory for studying Earth. Like Earth, Titan possesses the primary ingredients for life, namely energy, water and organics. Information from Titan will help scientists better understand the Earth‚Äôs origin, formative processes and development of life.
‚ÄúWe still don‚Äôt understand exactly how life began on Earth, so if we can understand how the fundamentals of these processes may be starting in some laboratory like Titan, it will help us understand the Earth a lot better,‚ÄĚ Radebaugh said.
In addition to analyzing images from space, Radebaugh also looks on planet earth for clues about the geology of other planets, moons and objects in the solar system. Two years ago Radebaugh scoured Antarctica for meteorites with the Antarctic Search for Meteorites (ANSMET) program. Through field work at Hawaiian volcanoes, she has also worked with students to utilize a technique for using a camcorder to measure eruption temperatures in the hope of learning more about volcanoes on Io, a moon of Jupiter.
Dec 15 10 12:16 AM
ScienceDaily (12 March 2010) ‚ÄĒ By precisely tracking NASA's Cassini spacecraft on its low swoops over Saturn's moon Titan, scientists have determined the distribution of materials in the moon's interior. The subtle gravitational tugs they measured suggest the interior has been too cold and sluggish to split completely into separate layers of ice and rock.
The finding, to be published in the March 12 issue of the journal Science, shows how Titan evolved in a different fashion from inner planets such as Earth, or icy moons such as Jupiter's Ganymede, whose interiors have split into distinctive layers.
"These results are fundamental to understanding the history of moons of the outer solar system," said Cassini Project Scientist Bob Pappalardo, commenting on his colleagues' research. Pappalardo is with NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We can now better understand Titan's place among the range of icy satellites in our solar system."
Scientists have known that Titan, Saturn's largest moon, is about half ice and half rock, but they needed the gravity data to figure out how the materials were distributed. It turns out Titan's interior is a sorbet of ice studded with rocks that probably never heated up beyond a relatively lukewarm temperature. Only in the outermost 500 kilometers (300 miles) is Titan's ice devoid of any rock, while ice and rock are mixed to various extents at greater depth.
"To avoid separating the ice and the rock, you must avoid heating the ice too much," said David J. Stevenson, one of the paper's co-authors and a professor of planetary science at the California Institute of Technology in Pasadena. "This means that Titan was built rather slowly for a moon, in perhaps around a million years or so, back soon after the formation of the solar system."
This incomplete separation of ice and rock makes Titan less like Jupiter's moon Ganymede, where ice and rock have fully separated, and perhaps more like another Jovian moon, Callisto, which is believed to have a mixed ice and rock interior. Though the moons are all about the same size, they clearly have diverse histories.
The Cassini measurements help construct a gravity map, which may help explain why Titan has a stunted topography, since interior ice must be warm enough to flow slowly in response to the weight of heavy geologic structures, such as mountains.
Creating the gravity map required tracking minute changes in Cassini's speed along a line of sight from Earth to the spacecraft as it flew four close flybys of Titan between February 2006 and July 2008. The spacecraft took paths between about 1,300 to 1,900 kilometers (800 to 1,200 miles) above Titan.
"The ripples of Titan's gravity gently push and pull Cassini along its orbit as it passes by the moon and all these changes were accurately recorded by the ground antennas of the Deep Space Network within 5 thousandths of a millimeter per second [0.2 thousandths of an inch per second] even as the spacecraft was over a billion kilometers [more than 600 million miles] away," said Luciano Iess, a Cassini radio science team member at Sapienza University of Rome in Italy, and the paper's lead author. "It was a tricky experiment."
The results don't speak to whether Titan has an ocean beneath the surface, but scientists say this hypothesis is very plausible and they intend to keep investigating. Detecting tides induced by Saturn, a goal of the radio science team, would provide the clearest evidence for such a hidden water layer.
A Cassini interdisciplinary investigator, Jonathan Lunine, said of his colleagues' findings, "Additional flybys may tell us whether the crust is thick or thin today." Lunine is with the University of Rome, Tor Vergata, Italy, and the University of Arizona, Tucson. "With that information we may have a better understanding of how methane, the ephemeral working fluid of Titan's rivers, lakes and clouds, has been resupplied over geologic time. Like the history of water on Earth, this is fundamental to a deep picture of the nature of Titan through time."
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech, manages the project for NASA's Science Mission Directorate in Washington. The Cassini orbiter was designed, developed and assembled at JPL. Cassini's radio science subsystem has been jointly developed by NASA and the Italian Space Agency (ASI).
More Cassini information is available, at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .
ScienceDaily (21 March 2008) ‚ÄĒ NASA's Cassini spacecraft has discovered evidence that points to the existence of an underground ocean of water and ammonia on Saturn's moon Titan. The findings made using radar measurements of Titan's rotation will appear in the March 21 issue of the journal Science.
"With its organic dunes, lakes, channels and mountains, Titan has one of the most varied, active and Earth-like surfaces in the solar system," said Ralph Lorenz, lead author of the paper and Cassini radar scientist at the Johns Hopkins Applied Physics Laboratory in Laurel, Md., "Now we see changes in the way Titan rotates, giving us a window into Titan's interior beneath the surface."
Members of the mission's science team used Cassini's Synthetic Aperture Radar to collect imaging data during 19 separate passes over Titan between October 2005 and May 2007. The radar can see through Titan's dense, methane-rich atmospheric haze, detailing never-before-seen surface features and establishing their locations on the moon's surface.
Using data from the radar's early observations, the scientists and radar engineers established the locations of 50 unique landmarks on Titan's surface. They then searched for these same lakes, canyons and mountains in the reams of data returned by Cassini in its later flybys of Titan. They found prominent surface features had shifted from their expected positions by up to 19 miles. A systematic displacement of surface features would be difficult to explain unless the moon's icy crust was decoupled from its core by an internal ocean, making it easier for the crust to move.
"We believe that about 62 miles beneath the ice and organic-rich surface is an internal ocean of liquid water mixed with ammonia," said Bryan Stiles of NASA's Jet Propulsion Laboratory (JPL) in, Pasadena, Calif. Stiles also is a contributing author to the paper.
The study of Titan is a major goal of the Cassini-Huygens mission because it may preserve, in deep-freeze, many of the chemical compounds that preceded life on Earth. Titan is the only moon in the solar system that possesses a dense atmosphere. [OTHER MOONS around Saturn have atmospheres, but are veiled very thinly compared to Titan.] The moon's atmosphere is 1.5 times denser than Earth's. Titan is the largest of Saturn's moons, bigger than the planet Mercury.
"The combination of an organic-rich environment and liquid water is very appealing to astrobiologists," Lorenz said. "Further study of Titan's rotation will let us understand the watery interior better, and because the spin of the crust and the winds in the atmosphere are linked, we might see seasonal variation in the spin in the next few years."
Cassini scientists will not have long to wait before another go at Titan. On March 25, just prior to its closest approach at an altitude of 620 miles, Cassini will employ its Ion and Neutral Mass Spectrometer to examine Titan's upper atmosphere. Immediately after closest approach, the spacecraft's Visual and Infrared Mapping Spectrometer will capture high-resolution images of Titan's southeast quadrant.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The mission is managed by JPL, a division of the California Institute of Technology in Pasadena. The Cassini orbiter also was designed, developed and assembled at JPL.
For information about Cassini visit: http://www.nasa.gov/cassiniSaturn's Moon Titan May Have Subsurface Ocean Of Hydrocarbons
Titan is also more squashed in its overall shape‚ÄĒlike a rubber ball pressed down by a foot‚ÄĒthan researchers had expected, said Howard Zebker, a Stanford geophysicist and electrical engineer involved in the work. The new findings may help explain the presence of large lakes of hydrocarbons at both of Titan's poles, which have been puzzling researchers since being discovered in 2007.
"Since the poles are squished in with respect to the equator, if there is a hydrocarbon 'water table' that is more or less spherical in shape, then the poles would be closer down to that water table and depressions at the poles would fill up with liquid," Zebker said. The shape of the water table would be controlled by the gravitational field of Titan, which is still not fully understood.
Hydrocarbons are the only materials on Titan's surface that would remain liquid at minus180 degrees Celsius, the average temperature of the moon's surface. Any water would be frozen, making it plausible that instead of groundwater, Titan would have the equivalent in hydrocarbons.
The research will be published in a paper in the journal Science.
Zebker, the lead author, and a group of colleagues have been making radar measurements of Titan's surface over the last four years using an instrument aboard the Cassini spacecraft, which is orbiting Saturn. Whenever Cassini passes close enough, they sweep beams of cloud-penetrating radar through Titan's thick atmosphere and across the surface. Using the radar data, they can calculate the surface elevations along the tracks of the sweep.
Combining more than 40 tracks across the surface, the researchers were able to calculate the three-dimensional shape of Titan.
Zebker said that there were theoretical reasons to expect that Titan was not a perfect sphere, but instead probably slightly oblate, or flattened, due to the centrifugal force from its rotation while orbiting Saturn. But the degree to which Titan is flattened exceeds what would be expected, based upon how close it is to Saturn and its roughly 16-day orbit.
It also turns out that Titan is not flattened uniformly. By way of analogy, if you were to put your foot on a rubber ball and press down, the ball would bulge out equally on all sides in the directions perpendicular to the downward force from your foot.
But the bulge of Titan is asymmetrical. The longest axis is oriented so that it points toward Saturn, a result of tidal forces from the planet. The shortest axis runs through the poles. And the other axis, oriented in the direction in which Titan orbits Saturn, is intermediate in length.
"While some asymmetry is expected from Saturn's gravitational pull, there is obviously something going on that causes Titan to have a different shape than expected," Zebker said.
There are several possible explanations for Titan's deformity. It might be that when the shape of the moon was determined, it was in an orbit closer to Saturn. "Another is that there are active geophysical processes occurring inside Titan that further distort the shape," Zebker said. "There are probably many other explanations as well, but we don't have enough information from this one experiment to be able to distinguish those."
Active geophysical processes might help account for another of Titan's oddities.
Zebker said that if you look at images of the surface of Titan, you see surface features that look every bit like mountains on Earth but don't have the high elevations compared to the plains stretching out around them.
"One of the really surprising finds that we have from this, is that the largest apparent continent is lower than the average elevation on Titan, as opposed to higher than the average elevation, as we have on the Earth," Zebker said.
"My favorite explanation is that the material that forms the mountains is simply more dense than the material surrounding them," he said. That would result in the mountains pushing down the surrounding crust, effectively putting the mountains in a basin of their own creation.
On Earth, the situation is the reverse: The crust that lies under the oceans is denser than the material that makes up the continental crust, where mountain ranges are built up.
"The things that we would expect to exist on the surface of Titan would either be solid hydrocarbon materials, essentially frozen ethane and methane, and that is fairly light, and then frozen water ice, which is denser," Zebker said. "If the mountains are composed of water ice and the plain features in between are composed of these solid hydrocarbons, that could lead to this kind of a situation."
Zebker said that research currently being conducted by other scientists to decipher the gravity field of Titan should help resolve some of the questions raised by his team's latest work. But he's holding off making any predictions.
"All of it surprises me because you never know what you are going to see," he said.
Dec 18 10 1:50 AM
Mono Lake is home to arsenic-eating bacteria, recently discovered by NASA.
NASA scientists recently announced they had discovered an organism that uses arsenic instead of phosphorus in its metabolism. The geologist Dirk Schulze-Makuch talked to SPIEGEL about the implications of the findings and the likelihood that life could exist on other planets.
SPIEGEL: NASA scientists have discovered strange bacteria in California's Mono Lake. The microbes incorporate arsenic, which is usually poisonous for life forms, into their cells. Are they originally from another planet?
SPIEGEL: What does this discovery mean for the search for extraterrestrial life-forms?
Schulze-Makuch: The arsenic bacteria help us broaden our horizons. If we can find such exotic organisms on Earth, what strange beings could exist on other planets? We have to free ourselves from the idea that life-forms will resemble what we know from Earth.
SPIEGEL: What differences can you imagine?
Schulze-Makuch: Our fixation with the idea that oxygen is essential to life is already short-sighted. This aggressive element inflicts damage to our cells in the form of free radicals. Maybe organisms elsewhere in space have found a gentler alternative. When we send space probes to other worlds, we should expect the unexpected. Life can appear anywhere: in poisonous seas or in hot clouds.
SPIEGEL: Where could the resistant arsenic bacteria thrive?
Schulze-Makuch: Arsenic-eating microbes would probably feel very at home on our neighboring planet, Mars. Its conditions are well suited to them. Measurements collected by landing robots on Mars can indeed be interpreted as evidence of bacterial life. However, it could be that any life-forms on Mars aren't actually aliens, but are related to us.
SPIEGEL: How do you mean?
Schulze-Makuch: Almost 4 billion years ago, Mars was a planet well suited to sustaining life, with massive rivers and lakes. Back then, the first primitive organisms appeared on Earth. These single-cell life-forms probably made it to our neighboring planet Mars by way of meteorites and established themselves there. It is possible that descendents of these primitive bacteria could have survived in nooks and crannies on Mars until today. Equally fascinating is the opposite possibility: Life could have started on Mars and then, via a meteorite, made its way to Earth. That would raise the question: Are we all Martians?
SPIEGEL: Which planet in our solar system is most likely to sustain life which contrasts significantly from life on Earth?
Schulze-Makuch: The distant Titan, a moon of Saturn, seems completely foreign to us. Its surface temperature is minus 160 degrees Celsius (minus 256 degrees Fahrenheit), and its atmosphere contains no oxygen. Instead of water, its lakes are filled with liquid natural gas. Methane rains from the sky, and it looks like the aftermath of an oil spill in the Antarctic. If we were to discover life there, it would certainly look completely different from life as we know it on Earth.
SPIEGEL: What are the chances of that?
Schulze-Makuch: Surprisingly good! On the Caribbean island of Trinidad, there is a natural asphalt reserve called Pitch Lake, which is fed by oleaginous substances from the Earth's crust. It's a tourist attraction. Its conditions are similar to that of a lake on Titan. My team and I recently took samples to search for traces of life.
SPIEGEL: And what results did you get?
SPIEGEL: But that is hardly proof.
Schulze-Makuch: Of course not. We will first get clarity when a robot mission explores Titan. The discovery of the arsenic bacteria and the asphalt bacteria do show, however, that when life has found its way to a planet then it will find a biochemical way to survive. The only problem is that we unfortunately don't know exactly how life began on Earth -- let alone how it could develop on another planet.
Interview conducted by Olaf Stampf
Jan 6 11 11:40 PM
It's long been speculated that the largest moon of Saturn, Titan, has large volcanoes made of ice. In 2005, it was thought that one of these ice volcanoes had been discovered, but further studies showed that it wasn't one after all. These large ice volcanoes are referred to as cryovolcanoes but direct observations of them on Titan have always been quite difficult due to its hazy atmosphere, which makes images fuzzy or blurry. The existence of ice volcanoes is not a new idea as scientists have already confirmed that they exist on another of Saturn's moons, Enceladus. Instead of red hot molten lava volcanoes, like we have here on Earth, these cryovolcanoes spew jets of icy material into the atmosphere wherever they are located.
Composite view of Titan built thanks to Cassini's images taken on 9 October and 25 October 2006. (Credit: NASA/JPL/University of Arizona)
Recently, the Cassini probe has detected an over-4,000'-high mountain with what appears to be several large holes or pits‚ÄĒone of which is, astoundingly, almost a mile deep. The images that Cassini has provided us with also show a downward flow of material on the outer edges and faces of this mountain. Cassini has a variety of scientific instruments on board, including radar and infrared. When these tools are combined, scientists here on Earth can then develop three-dimensional topographic maps and surface composition analysis of Titan. It was first thought that some of these pits could in fact be impact craters from a distant past, but experts now think that is probably unlikely.
The image above (provided by NASA) shows a radar mapping image made by the Cassini spacecraft of a flyover area on Saturn's giant moon Titan showing an ice volcano. There's been ongoing debate about whether volcanoes exist on ice-rich moons in the outer solar system.
The Titan moon has long had a number of mysteries that we have not been able to explain. For example, we know that the moon has a very thick atmosphere that is rich in nitrogen but also carries a substantial amount of methane. The methane is what gives the giant moon its orange hue. It's known that methane can be produced by a number of different factors such as deterioration of organic debris or volcanoes, and scientists have been puzzled because it is thought that methane would essentially break down due to sunlight and radiation from space.ÔŅĹ This means that there is something else fueling the supply. Scientists now think that this cryrovolcanos on the surface may be the culprit of the smoggyness in the atmosphere. A cyrovolcano may be spewing large amounts of methane into Titan's atmosphere, but the Cassini team isn't completely sure, they believe it might be mostly water and ammonium or lots of hydrocarbons. Randy Kirk, a team member and geophysicist of the U.S. Geological Survey,ÔŅĹ states that "this offers us one way to get at that interior."
There are, of course, still lots of unanswered questions surrounding the new Cassini images and Titan itself. Scientists have not determined if this is an actual volcano and they have yet to determine the true source of the replenished methane on Titan but let's hope that new studies will confirm this. If this is confirmed, it will finally put to rest some of the debates that have been going on for decades.ÔŅĹWhere does the energy of these volcanoes come from? The energy of volcanoes on the earth comesÔŅĹlargelyÔŅĹfrom the fact that the earth's core is radioactive. Long-lived radioactive elements continually heat up the earth's core for billions of years. But on Titan and other moons, most likely the energy source comes from gravitational tidal forces coming from the mother planet. For example, Io is a moon of Jupiter which has perhaps the largest number of active volcanoes. The energy of Io's volcanoes probably comes from the fact that it is being continually squeezed by Jupiter's great gravitational force, creating friction, which then causes the core to heat up. Something similar may happen for Titan.
Clip is based on data from NASA's Cassini spacecraft and shows a flyover of an area of Saturn's moon Titan known as Sotra Facula. Scientists believe Sotra is the best case for an ice volcano -- or cryovolcano -- region on Titan. Credit: NASA/JPL-Caltech/USGS/University of Arizona
by Anne Minard on 06 August 2009
Artist's impression of hydrocarbon pools, icy and rocky terrain on the surface of Saturn's largest moon Titan. Image credit: Steven Hobbs (Brisbane, Queensland, Australia)
It‚Äôs more than a billion kilometers (759 million miles) away, but the more astronomers learn about Titan, the more it looks like Earth.
That‚Äôs the theme of two talks happening this week at the International Astronomical Union meeting in Rio de Janeiro,†Brazil. Two NASA researchers,†Rosaly Lopes and†Robert M. Nelson of the†Jet Propulsion Laboratory in Pasadena, California, are reporting that weather and geology have very similar actions on Earth and Titan ‚ÄĒ even though Saturn‚Äôs moon is, on average, 100 degrees C (212 degrees F) colder than Antarctica (and certainly much more frigid than either California or Brazil; lucky astronomers).
The researchers are also reporting a tantalizing clue in the search for life: Titan hosts chemistry much like pre-biotic conditions on Earth.
Wind, rain, volcanoes, tectonics and other Earth-like processes all sculpt features on Titan‚Äôs complex and varied surface ‚ÄĒ except, according to additional research being presented at the meeting, †scientists think the ‚Äúcryovolcanoes‚ÄĚ on Titan eject cold slurries of water-ice and ammonia instead of scorching hot magma.
‚ÄúIt is really surprising how closely Titan‚Äôs surface resembles Earth‚Äôs,‚ÄĚ Lopes said.†‚ÄĚIn fact, Titan looks more like the Earth than any other body in the Solar System, despite the huge differences in temperature and other environmental conditions.‚ÄĚ
The joint NASA/ESA/ASI Cassini-Huygens mission has revealed details of Titan‚Äôs geologically young surface, showing few impact craters, and featuring mountain chains, dunes and even ‚Äúlakes.‚ÄĚ The RADAR instrument on the Cassini orbiter has now allowed scientists to image a third of Titan‚Äôs surface using radar beams that pierce the giant moon‚Äôs thick, smoggy atmosphere. There is still much terrain to cover, as the aptly named Titan is one of the biggest moons in the Solar System, larger than the planet Mercury and approaching Mars in size.
New Cassini mosaic showing a dried-out lake at Titan's south pole.
Titan has long fascinated astronomers as the only moon known to possess a thick atmosphere, and as the only celestial body other than Earth to have stable pools of liquid on its surface. The many lakes that pepper the northern polar latitudes, with a scattering appearing in the south as well, are thought to be filled with liquid hydrocarbons, such as methane and ethane.
On Titan, methane takes water‚Äôs place in the hydrological cycle of evaporation and precipitation (rain or snow) and can appear as a gas, a liquid and a solid. Methane rain cuts channels and forms lakes on the surface and causes erosion, helping to erase the meteorite impact craters that pockmark most other rocky worlds, such as our own Moon and the planet Mercury.
Another Cassini instrument called the Visual and Infrared Mapping Spectrometer (VIMS)†had previously detected an area, called Hotei Regio, with a varying infrared signature, suggesting the temporary presence of ammonia frosts that subsequently dissipated or were covered over. Although the ammonia does not stay exposed for long, models show that it exists in Titan‚Äôs interior, indicating that a process is at work delivering ammonia to the surface. RADAR imaging has indeed found structures that resemble terrestrial volcanoes near the site of suspected ammonia deposition.
Nelson said new infrared images of the region, also presented at the IAU, ‚Äúprovide further evidence suggesting that cryovolcanism† has deposited ammonia onto Titan‚Äôs surface. It has not escaped our attention that ammonia, in association with methane and nitrogen, the principal species of Titan‚Äôs atmosphere, closely replicates the environment at the time that life first emerged on Earth. One exciting question is whether Titan‚Äôs chemical processes today support a prebiotic chemistry similar to that under which life evolved on Earth?‚ÄĚ
Many Titan researchers hope to observe Titan with Cassini for long enough to follow a change in seasons. Lopes thinks that the hydrocarbons there likely evaporated because this hemisphere is experiencing summer. When the seasons change in several years and summer returns to the northern latitudes, the lakes so common there may evaporate and end up pooling in the south.
Lead image caption: Artist‚Äôs impression of hydrocarbon pools, icy and rocky terrain on the surface of Saturn‚Äôs largest moon Titan. Image credit: Steven Hobbs (Brisbane, Queensland, Australia)
Source: International Astronomical Union (IAU)
Jan 7 11 2:05 PM
ScienceDaily (Oct. 1, 2010) ‚ÄĒ The northern hemisphere of Saturn's moon Titan is set for mainly fine spring weather, with polar skies clearing since the equinox in August last year. The visual and infrared mapping spectrometer (VIMS) aboard NASA's Cassini spacecraft has been monitoring clouds on Titan regularly since the spacecraft entered orbit around Saturn in 2004.
Now, a group led by S√©bastien Rodriguez, a Cassini VIMS team collaborator based at Universit√© Paris Diderot, France, has analyzed more than 2,000 VIMS images to create the first long-term study of Titan's weather using observational data that also includes the equinox. Equinox, when the sun shone directly over the equator, occurred in August 2009.
Rodriguez presented the results and new images at the European Planetary Science Congress in Rome on Sept. 22.
Though Titan's surface is far colder and lacks liquid water, this moon is a kind of "sister world" to Earth because it has a surface covered with organic material and an atmosphere whose chemical composition harkens back to an early Earth. Titan has a hydrological cycle similar to Earth's, though Titan's cycle depends on methane and ethane rather than water.
A season on Titan lasts about seven Earth years. Rodriguez and colleagues observed significant atmospheric changes between July 2004 (early summer in Titan's southern hemisphere) and April 2010 (the very start of northern spring). The images showed that cloud activity has recently decreased near both of Titan's poles. These regions had been heavily overcast during the late southern summer until 2008, a few months before the equinox.
Over the past six years, the scientists found that clouds clustered in three distinct latitude regions of Titan: large clouds at the north pole, patchy clouds at the south pole and a narrow belt around 40 degrees south. "However, we are now seeing evidence of a seasonal circulation turnover on Titan -- the clouds at the south pole completely disappeared just before the equinox and the clouds in the north are thinning out," Rodriguez said. "This agrees with predictions from models and we are expecting to see cloud activity reverse from one hemisphere to another in the coming decade as southern winter approaches."
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate, Washington, D.C. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.
More details can be found at: http://www.europlanet-eu.org/outreach/index.php?option=com_content&task=view&id=288&Itemid=41
For more information about Cassini, go to: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .
ScienceDaily (June 4, 2009) ‚ÄĒ Cloud chasers studying Saturn's moon Titan say its clouds form and move much like those on Earth, but in a much slower, more lingering fashion.
Their forecast for Titan's early autumn -- warm and wetter.
Scientists with NASA's Cassini mission have monitored Titan's atmosphere for three-and-a-half years, between July 2004 and December 2007, and observed more than 200 clouds. They found that the way these clouds are distributed around Titan matches scientists' global circulation models. The only exception is timing -- clouds are still noticeable in the southern hemisphere while fall is approaching.
"Titan's clouds don't move with the seasons exactly as we expected," said Sebastien Rodriguez of the University of Paris Diderot, in collaboration with Cassini visual and infrared mapping spectrometer team members at the University of Nantes, France. "We see lots of clouds during the summer in the southern hemisphere, and this summer weather seems to last into the early fall. It looks like Indian summer on Earth, even if the mechanisms are radically different on Titan from those on Earth. Titan may then experience a warmer and wetter early autumn than forecasted by the models."
On Earth, abnormally warm, dry weather periods in late autumn occur when low-pressure systems are blocked in the winter hemisphere. By contrast, scientists think the sluggishness of temperature changes at the surface and low atmosphere on Titan may be responsible for its unexpected warm and wet, hence cloudy, late summer.
As summer changes to fall at the equinox in August 2009, Titan's clouds are expected to disappear altogether. But, circulation models of Titan's weather and climate predict that clouds at the southern latitudes don't wait for the equinox and should have already faded out since 2005. However, Cassini was still able to see clouds at these places late in 2007, and some of them are particularly active at mid-latitudes and the equator.
Titan is the only moon in our solar system with a substantial atmosphere, and its climate shares Earth-like characteristics. Titan's dense, nitrogen-methane atmosphere responds much more slowly than Earth's atmosphere, as it receives about 100 times less sunlight because it is 10 times farther from the sun. Seasons on Titan last more than seven Earth years.
Scientists will continue to observe the long-term changes during Cassini's extended mission, which runs until the fall of 2010. Cassini is set to fly by Titan on May 6.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The visual and infrared mapping spectrometer team is based at the University of Arizona.
Feb 3 11 3:24 AM
Astronomers identify six planets orbiting a sun ‚Äď the most similar system to our own yet discovered ‚Äď 2,000 light-years away
Astronomers have discovered a planetary system made up of six planets orbiting a Sun-like star that is more than 2,000 light years from Earth. It is the largest number of planets found so far around a single star.
More than 100 planets have been seen outside our solar system, but most are Jupiter-like gas giants, and almost all are in single-planet systems.
Jack Lissauer, a scientist at Nasa's Ames research centre in California and a lead author on a paper published tomorrow in the journal Nature, said that the Kepler-11 finding was "the biggest thing in exoplanets since the discovery of 51 Pegasi B, the first exoplanet, back in 1995".
The five inner planets of the Kepler-11 system are between 2.3 and 13.5 times the mass of the Earth, and make their orbits in less than 50 days. All of them are so close to their star that their orbits would fit within that of Mercury in our solar system. The sixth planet has an orbital period of 118 days and sits at a distance from its star that is half the Sun-Earth distance. Lissauer said it was unexpected to find a system where planets could be so close to one another and there could be so many of them on such a flat plane. "The Kepler-11 system is flatter than a CD," he said. "If placed within our solar system, Kepler-11's six planets would lie between those of the sun's innermost planets, Mercury and Venus."
Astronomers found the planets by analysing data from the Kepler space telescope. Every time a planet passes between its star and an observer, it is said to be transiting; by measuring how often and how much the star dimmed in brightness as planets crossed in front of it, they were able to measure the size and density of the planets.
To calculate masses, astronomers measured the slight variations in the orbital periods of the planets caused by gravitational interactions among them.
Most of the volume of the Kepler-11 plenats is made of light elements, according to Jonathan Fortey of the University of California, Santa Cruz. "It looks like the inner two could be mostly water, with possibly a thin skin of hydrogen-helium gas on top, like mini-Neptunes. The ones farther out have densities less than water, which seems to indicate significant hydrogen-helium atmospheres."
Though none of the six planets found resemble Earth, Lissauer did not discount the idea that there could be more planets orbiting the star, one of which could be more Earth-like. The sixth planet, for example, is at a temperature of around 120C-170C, so any planets further out could be cooler. "It's possible there could be an Earth-sized planet in the habitable zone, because we're not seeing any of these big planets out there," he said.
Feb 4 11 2:28 AM
Astronomers have identified some 54 new planets where conditions may be suitable for life.
Five of the candidates are Earth-sized.
The announcement from the Kepler space telescope team brings the total number of exoplanet candidates they have identified to more than 1,200.
The data release also confirmed a unique sextet of planets around a single star and 170 further solar systems that include more than one planet circling far-flung stars.
The Kepler telescope was conceived to hunt for exoplanets, staring into a small, fixed patch of the sky in the direction of the constellations Cygnus and Lyra.
It looks for the minuscule dimming of light that occurs when an exoplanet passes in front of its host star. Kepler spots "candidate" planets, which typically are confirmed by ground-based observations to confirm their existence.
In just its first few months of operation, as a paper posted to the Arxiv server reports, Kepler has spotted 68 Earth-sized candidates, 288 so-called "super-Earths" that are up to twice Earth's size, 662 that are Neptune-sized, and 184 that are even larger.
On Wednesday, members of the team announced it had confirmed the Kepler-11 solar system, comprising six large exoplanets tightly circling an eight billion-year-old star that lies about 2,000 light-years away.
"The fact that we've found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting sun-like stars in our galaxy," said William Borucki, who heads Kepler's science programme at Nasa's Ames Research Center.
"We went from zero to 68 Earth-sized planet candidates and zero to 54 candidates in the habitable zone, some of which could have moons with liquid water."
The bountiful nature of the data from just a few months of observing time from Kepler makes profound suggestions about the preponderance of exoplanets in general, and about the existence of multiple planets around single stars in particular.
In a separate paper, team members outlined how the Kepler candidates include 115 stars that host a pair of planets, 45 with three, eight stars with four, one with five planets, and Kepler-11, which hosts six.
"Even in first four months of Kepler data, a rich population of multiples appeared, and we recognised this was going to be a very important discovery," David Latham, of the Harvard-Smithsonian Center for Astrophysics, told BBC News.
Feb 5 11 1:30 AM
ScienceDaily (Feb. 3, 2011) ‚ÄĒ Every day is a bad-air day on Saturn's largest moon, Titan. Blanketed by haze far worse than any smog belched out in Los Angeles, Beijing or even Sherlock Holmes's London, the moon looks like a dirty orange ball. Described once as crude oil without the sulfur, the haze is made of tiny droplets of hydrocarbons with other, more noxious chemicals mixed in. Gunk.
Icky as it may sound, Titan is really the rarest of gems: the only moon in our solar system with an atmosphere worthy of a planet. This atmosphere comes complete with lightning, drizzle and occasionally a big, summer-downpour style of cloud made of methane or ethane -- hydrocarbons that are best known for their role in natural gas.
Now, thin, wispy clouds of ice particles, similar to Earth's cirrus clouds, are being reported by Carrie Anderson and Robert Samuelson at NASA's Goddard Space Flight Center in Greenbelt, Md. The findings, published February 1 in Icarus, were made using the Composite Infrared Spectrometer (CIRS) on NASA's Cassini spacecraft.
Unlike Titan's brownish haze, the ice clouds have the pearly white appearance of freshly fallen snow. Their existence is the latest clue to the workings of Titan's intriguing atmosphere and its one-way "cycle" that delivers hydrocarbons and other organic compounds to the ground as precipitation. Those compounds don't evaporate to replenish the atmosphere, but somehow the supply has not run out (yet?).
"This is the first time we have been able to get details about these clouds," says Samuelson, an emeritus scientist at Goddard and the co-author of the paper. "Previously, we had a lot of information about the gases in Titan's atmosphere but not much about the [high-altitude] clouds."
Puffy methane and ethane clouds had been found before by ground-based observers and in images taken by Cassini's imaging science subsystem and visual and infrared mapping spectrometer. Compared to those clouds, these are much thinner and located higher in the atmosphere. "They are very tenuous and very easy to miss," says Anderson, the paper's lead author. "The only earlier hints that they existed were faint glimpses that NASA's Voyager 1 spacecraft caught as it flew by Titan in 1980."
Out on a Limb
Even before Voyager 1 reached Titan, scientists knew the moon was wrapped in a thick atmosphere that probably contained hydrocarbons. Part of that atmosphere, Voyager found, is a haze so smothering that it hides every bit of the moon's surface.
Only a small amount of visible light penetrates this haze, or aerosol, so studies rely on instruments that operate at wavelengths beyond human sight. This is how Voyager learned that Titan's atmosphere is made mostly of nitrogen, as is Earth's. Unlike Earth's atmosphere, though, Titan's has neither oxygen nor water to speak of. Instead, it contains small amounts of organic materials, including members of the hydrocarbon family such as methane, ethane and propane.
Voyager also picked up indications that Titan's stratosphere, the second-lowest layer of its atmosphere, harbored "ices made from some exotic organic compounds," Samuelson says. "At the time, that was about all we could tell."
Fast-forward a quarter-century to mid-2006, past decades of research conducted from telescopes, past Cassini's arrival at Saturn, past the European Space Agency's Huygens probe landing on Titan and taking the first pictures of the surface, past the discovery of the methane and ethane clouds. At this point, Cassini continues to orbit Saturn and visit Titan and other moons periodically.
More than a half-dozen hydrocarbons have been identified in gas form in Titan's atmosphere, but many more probably lurk there. Researchers worldwide are looking for them, including Anderson and Samuelson, who are using the CIRS (pronounced "sears") instrument on Cassini.
Pinpointing the altitudes where such gases turn into ices is painstaking work. The researchers scan up and down the atmosphere, pausing at each altitude to catalog a slew of signals that have to be teased apart later so that the molecules can be identified. "You can learn a lot about a compound, even if you have no idea what it is, by looking at how it is distributed vertically," says Anderson. "Where does it accumulate? Where does it dissipate? How thick is the boundary? Is there layering going on?"
Anderson and Samuelson start a series of observations near Titan's north pole, at roughly the same latitudes Voyager looked at, 62 ¬įN and 70 ¬įN. On Earth, these would fall just inside and outside the ring for the Arctic Circle.
The team focuses on the observations made when CIRS is positioned to peer into the atmosphere at an angle, grazing the edge of Titan. This path through the atmosphere is longer than the one when the spacecraft looks straight down at the surface. Planetary scientists call this "viewing on the limb," and it raises the odds of encountering enough molecules of interest to yield a strong signal.
It works. When the researchers comb through their data, they succeed in separating the telltale signatures of ice clouds from the aerosol. "These beautiful, beautiful ice clouds are optically thin, and they're diffuse," says Anderson. "But we were able to pick up on them because of the long path lengths of the observations."
In addition to spotting the clouds, the researchers gather enough information to measure the sizes of the ice particles. The results get reported in a January 2010 Icarus paper by Anderson, Samuelson, their Goddard colleague Gordon Bjoraker and Richard Achterberg, a University of Maryland staff member working at Goddard.
"That was convincing evidence," Anderson says. "What Voyager had seen was real."
That Sinking Feeling
Clouds on Titan can't be made from water because of the planet's extreme cold. "If Titan has any water on the surface, it would be solid as a rock," says Goddard's Michael Flasar, the Principal Investigator for CIRS.
Instead, the key player is methane. The action starts high in the atmosphere, where some of the methane gets broken up and reforms into ethane and other hydrocarbons, or combines with nitrogen to make materials called nitriles. Any of these compounds can probably form clouds if enough accumulates in a sufficiently cold area.
The cloud-forming temperatures occur in the "cold, cold depths of Titan's stratosphere," says Anderson. Researchers think that the compounds get moved downward by a constant stream of gas flowing from the pole in the warmer hemisphere to the pole in the colder hemisphere. There, the gas sinks.
This circulation pattern steals so much gas from the warmer hemisphere that researchers can measure the imbalance. The influx of all this gas gives the colder hemisphere more clouds. "At colder temperatures, more gas will condense anyway," Anderson explains, "and on top of that, the atmosphere dumps a whole bunch of extra gas there."
She and Samuelson think this is why the ice clouds were first spotted in the north. When Voyager flew by in November 1980, the north had just crossed from winter into spring. And the north was in mid-winter when the team conducted their early observations. (One Titan year lasts 29-1/2 Earth years, so spring came again to Titan's north in August 2009.)
Still, the team figured, the south shouldn't lack ice clouds; it should just have fewer of them. "For 30 years, Bob [Samuelson] had been saying that these clouds should exist in the southern hemisphere," says Anderson, "so we decided to look."
The team checked Titan's southern hemisphere (at 58 ¬įS latitude) and both sides of the equator (15 ¬įN and 15 ¬įS). Sure enough, they spotted clouds in all three locations. And as predicted, the clouds in the north were more plentiful -- in fact, three times more plentiful -- than those just south of the equator.
"The fact that the clouds are more enhanced at the cold polar region is a promising sign," says Flasar. "It strengthens this idea that the molecules making up these clouds are being carried downward by this global circulation."
Part of Titan's allure has long been the organic compounds in the atmosphere, especially because some are thought to be involved in the events that led to life on Earth. One of those is cyanoacetylene, a member of the nitrile family. The compound's distinctive signature made it the first to be picked up in the northern ice clouds by Voyager 1 and by Anderson and Samuelson.
To make a connection between these molecules and life isn't the point for Anderson, though. "I just love ices and aerosols," she says, "and Titan is this great natural laboratory for studying them."
As the researchers continue to identify compounds in Titan's atmosphere, the next likely candidate for an ice is hydrogen cyanide, a nitrile with an earthly reputation as a poison. In the aerosol, the team is investigating an intriguing feature in the data that seems to represent larger hydrocarbons than anybody has identified before, according to Samuelson. Early clues suggest the signature could indicate polycyclic aromatic hydrocarbons (PAHs), which typically get noticed on Earth as pollutants released by the burning of fossil fuels. In space, PAHs form in the regions where stars are born and die.
Each nugget of information like this is helping scientists piece together the life cycle and ultimate fate of Titan's hydrocarbons, which never reenter the atmosphere via evaporation. "They fall to the surface, and it's a dead end," says Samuelson, "and yet Titan's atmosphere still has methane in it. We are trying to find out why."
The Great Switcheroo
At first, Titan's frozen nitriles seem entirely unrelated to Earth clouds. Even putting aside their exotic ingredients, they form much higher in the atmosphere: at altitudes of about 30 to 60 miles (in the stratosphere) versus no more than 11 miles (in the troposphere) for nearly all Earth clouds.
But Earth does have a few polar stratospheric clouds that appear over Antarctica (and sometimes in the Arctic) during winter. These clouds form in the exceptionally cold air that gets trapped in the center of the polar vortex, a fierce wind that whips around the pole high in the stratosphere. This is the same region where Earth's ozone hole is found.
Titan has its own polar vortex and may even have a counterpart to our ozone hole. The degree of similarity is intriguing, says Flasar, given the different compositions and chemistries of the stratospheric clouds on Earth versus Titan.
"We are starting to find out how similar Titan's clouds are to Earth's," says Samuelson. "How do they compare? How do they not compare?"
The big test of scientists' understanding of Titan's atmosphere will come in 2017, when summer comes to the north and the south plunges into winter. "We expect to find a complete reversal in the circulation of gas then," says Anderson. "The gas should start to flow from the north to the south. And that should mean most of the high-altitude ice clouds will be in the southern hemisphere."
Other major changes are in store for Titan then, Flasar adds, including the disappearance of the fierce winds around the north pole. "The big question is: will the vortex go out with a bang or whimper?" he says. "On Earth, it goes out with a bang. It's very dramatic. But on Titan, maybe the vortex just gradually fizzles out like the smile of the Chesire cat."
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA/Goddard Space Flight Center.
Feb 13 11 11:19 AM
Feb 20 11 2:08 PM
WASHINGTON ‚Äď Scientists have estimated the first cosmic census of planets in our galaxy and the numbers are astronomical: at least 50 billion planets in the Milky Way.
At least 500 million of those planets are in the not-too-hot, not-too-cold zone where life could exist. The numbers were extrapolated from the early results of NASA's planet-hunting Kepler telescope.
Kepler science chief William Borucki says scientists took the number of planets they found in the first year of searching a small part of the night sky and then made an estimate on how likely stars are to have planets. Kepler spots planets as they pass between Earth and the star it orbits.
So far Kepler has found 1,235 candidate planets, with 54 in the Goldilocks zone, where life could possibly exist. Kepler's main mission is not to examine individual worlds, but give astronomers a sense of how many planets, especially potentially habitable ones, there are likely to be in our galaxy. They would use the one-four-hundredth of the night sky that Kepler is looking at and extrapolate from there.
Borucki and colleagues figured one of two stars has planets and one of 200 stars has planets in the habitable zone, announcing these ratios Saturday at the American Association for the Advancement of Science annual conference in Washington. And that's a minimum because these stars can have more than one planet and Kepler has yet to get a long enough glimpse to see planets that are further out from the star, like Earth, Borucki said.
For example, if Kepler were 1,000 light years from Earth and looking at our sun and noticed Venus passing by, there's only a one-in-eight chance that Earth would also be seen, astronomers said.
To get the estimate for the total number of planets, scientists then took the frequency observed already and applied it to the number of stars in the Milky Way.
For many years scientists figured there were 100 billion stars in the Milky Way, but last year a Yale scientist figured the number was closer to 300 billion stars.
Either way it shows that Carl Sagan was right when he talked of billions and billions of worlds, said retired NASA astronomer Steve Maran, who praised the research but wasn't part of it.
And that's just our galaxy. Scientists figure there are 100 billion galaxies.
Borucki said the new calculations lead to worlds of questions about life elsewhere in the cosmos. "The next question is why haven't they visited us?"
And the answer? "I don't know," Borucki said.
Kepler site: http://kepler.nasa.gov/
Mar 2 11 9:01 AM
The mystery of how the building blocks of biology came to be on Earth may finally have been solved
By Steve Connor
Tuesday, 01 March 2011
An artist's impression of the heavy bombardment period
As scientific mysteries go, this is the big one. How did life on Earth begin? Not how did life evolve, but how did it start in the first place? What was the initial spark that lit the fire of evolution?
Charles Darwin solved the mystery of life's wondrous diversity with his theory of natural selection. But even he was flummoxed by the ultimate mystery of mysteries: what led to the origin of life itself?
In trying to answer the problem, scientists have turned to the stars, or at least the "builders' rubble" of meteorites and comets left over from the formation of our solar system some five billion years ago. These space rocks, they believe, could help to explain why life began here on Earth.
An analysis of the meteorites has revealed that these rocks can be induced, under high pressures and temperatures, to emit nitrogen-containing ammonia, a vital ingredient for the first self-replicating molecules that eventually led to DNA, the molecule at the heart of all life.
"These particular meteorites have been preserved in the ice and are found pristine ‚Äď that is, they show less terrestrial contamination," said Professor Sandra Pizzarello of Arizona State University, who led the meteorite study published in the Proceedings of the National Academy of Sciences.
"What is important is the finding of abundant ammonia. Nitrogen is an indispensable ingredient for the formation of the biopolymers, such as DNA, RNA and proteins, on which life depends, and any theory that tries to explain life's origin has to account for a supply of 'usable' nitrogen," Professor Pizzarello said. "Therefore, its direct delivery as ammonia and in relatively large amounts from the nearby asteroids could have found a 'prebiotic venue' on the early Earth."
Tests have also shown that the nitrogen in the ammonia released by the meteorite is composed of unusual isotopes, indicating an extraterrestial origin rather than contamination from a terrestrial source.
Professor Pizzarello and her colleagues believe that similar meteorites falling to Earth about 4 billion years ago could have produced a constant and replenishable supply of ammonia, and hence nitrogen, which was so necessary for the formation of the first self-replicating molecules.
Previous studies of fossilised microbes in ancient rocks have shown that primitive life must have existed at least 3.5 billion years ago. Yet little is known of the time before that when life originated, except that it must have been very inhospitable.
The planet was bathed in intense ultraviolet light which quickly destroys organic molecules, and was pummelled with meteorites during the "heavy bombardment period" from 4.5 billion to 3.8 billion years ago. However, this bombardment of meteorites may have actually come with a silver lining, given that many of these space rocks would have carried the relatively delicate organic molecules necessary for life to get started.
Earlier studies have already confirmed that meteorites contain many different kinds of organic molecules, such as the amino acids that make up proteins to the nucleobases that form the building blocks of DNA, the molecule of inheritance. But this is the first time that a meteorite has been shown to be capable of providing a plentiful supply of nitrogen-containing ammonia, said Caroline Smith, the curator of meteorites at the Natural History Museum in London.
"The early Earth was a very violent place. It was hot and did not have the oxygen we have now so it was not conducive for the presence of molecules needed for life," Dr Smith said.
"Obviously ammonia is an important constituent for the idea that meteorites and other cometary material helped to seed the Earth with the buildings blocks needed for life. It adds a further piece to the jigsaw puzzle."
Making an impact
* Scientists estimate between 40,000 and 60,000 tonnes of meteorites and other cosmic debris land on Earth each year. About four billion years ago, during the period of the "heavy bombardment" of the early Earth, the amount would have been much higher. Scientists study meteorites to understand the evolution of the solar system, but these lumps of space rock may also tell them something about the origin of life here on Earth, and possibly on other planets.
The Murchison meteorite
This large meteorite fell to Earth on 28 September 1969 near the town of Murchison in Victoria, Australia. It is one of the most studied meteorites and its value lies in the fact that it was found immediately after it landed, thus limiting the risks of terrestrial contamination that could confuse any chemical analysis. Exhaustive tests on the rock have revealed that it contains a rich variety of organic molecules, such as amino acids, which are the building blocks of proteins, and nucleobases, found in DNA, the vital molecule of inheritance. Many scientists believe that the meteorite provides strong evidence of an extraterrestrial origin of life's building blocks.
The ALH 84001 meteorite
This meteorite was found in 1984 in a region of Antarctica called Allan Hills. There is no dispute that it came from Mars and that it landed on Earth many thousands of years ago, but there is great controversy over claims made in 1996 by Nasa scientists that the meterorite shows evidence of fossilised life forms that may have originated on the Red Planet. The potato-sized rock contains traces of "microfossils" that could have come from extraterrestrial microbes, the Nasa scientists claimed. Others, however, question whether these traces of life exist.
Mar 11 11 2:19 PM
There are, of course, still lots of unanswered questions surrounding the new Cassini images and Titan itself. Scientists have not determined if this is an actual volcano and they have yet to determine the true source of the replenished methane on Titan but let's hope that new studies will confirm this. If this is confirmed, it will finally put to rest some of the debates that have been going on for decades.ÔŅĹWhere does the energy of these volcanoes come from? The energy of volcanoes on the earth comesÔŅĹlargelyÔŅĹfrom the fact that the earth's core is radioactive. Long-lived radioactive elements continually heat up the earth's core for billions of years. But on Titan and other moons, most likely the energy source comes from gravitational tidal forces coming from the mother planet. For example, Io is a moon of Jupiter which has perhaps the largest number of active volcanoes. The energy of Io's volcanoes probably comes from the fact that it is being continually squeezed by Jupiter's great gravitational force, creating friction, which then causes the core to heat up. Something similar may happen for Titan.
Mar 23 11 1:53 AM
Spring may bring methane showers to the deserts of Titan, Saturn‚Äôs largest moon. NASA‚Äôs Cassini spacecraft recently saw a large, dark puddle appear in the wake of a storm cloud at the moon‚Äôs dune-filled equator.
‚ÄúIt‚Äôs the only easy way to explain the observations,‚ÄĚ said planetary scientist Elizabeth Turtle of Johns Hopkins University Applied Physics Laboratory, lead author of a study March 18 in Science. ‚ÄúWe‚Äôre pretty confident that it has just rained on Titan.‚ÄĚ
Aside from Earth, Titan is the only world known to have liquid lakes, clouds and a weather cycle to move moisture between them. But on chilly Titan, where temperatures plunge to -297 degrees Fahrenheit, the frigid lakes are filled with liquid methane and ethane, not water.
Titan‚Äôs lakes are also exclusively confined to the poles. The moon‚Äôs dry central regions are covered in rippling dunes and arid deserts.
But the dunes are crisscrossed by a network of dry channels, suggesting a wetter past. In 2006, Cassini observations showed hints of drizzle at the equator, but not enough rain to explain the riverbeds.
‚ÄúSo the question was, ‚ÄėWhen was the last rainfall near the equator of Titan?‚Äô‚ÄĚ said planetary scientist Tetsuya Tokano of the University of Cologne in Germany, who was not involved in the new work. Some researchers suggested that the rivers were a relic of a bygone era, or carved by things other than rain.
‚ÄúThis observation by Turtle et al. showed for the first time that there is rainfall on present Titan, not merely millions of years ago but at the present Titan,‚ÄĚ Tokano said. ‚ÄúThis is extraordinary.‚ÄĚ
In the new study, Turtle‚Äôs team describes a large cloud system moving eastward across Titan‚Äôs equator on Sept. 27, 2010. By October, observations show, a dune field called Belet that lies east of the clouds suddenly darkened. The dark patch extended for more than 190,000 square miles, and started fading fast. Some spots that were dark on Oct. 14 were bright again by Oct. 29, and even more bright spots were visible on Jan. 15.
Turtle thinks the shadow is wet ground after rainfall, like a sidewalk darkened by a shower. Titan‚Äôs winds aren‚Äôt strong enough to wreak such sudden or vast changes, she says, and it‚Äôs doubtful that the kind of explosive volcanic activity that could explain the dark patch is possible on Titan.
It‚Äôs not clear how much rain fell, she adds. Some areas could have flooded or sustained small puddles, but it may just be that the surface got wet.
The showers were probably prompted by Titan‚Äôs changing seasons. Cassini has been orbiting Saturn since 2004, but since a full year on Saturn ‚ÄĒ and therefore all its moons ‚ÄĒ lasts 29 Earth years, the spacecraft has only observed one 7-year season on Titan. Astronomers saw storms and rain at Titan‚Äôs south pole during the summer, and then the clouds cleared after the spring equinox in August 2009.
‚ÄúIt‚Äôs kind of the equivalent on Titan right now of early April, just into northern spring,‚ÄĚ Turtle said. ‚ÄúWhat we think triggered this huge storm is that the weather patterns are seasonal.‚ÄĚ Major cloud patterns move north as the southern summer ends, similar to the way they do on Earth, she says. The only difference is, Earth‚Äôs tropics sustain rain clouds year round. On Titan, the equator may see rain only a few times a year.
The difference comes, at least in part, from Titan‚Äôs leisurely rotation rate, Tokano said. Titan takes 16 Earth days to rotate once, meaning its atmospheric circulation patterns are somewhat more simple. Titan‚Äôs clouds shift quickly from north to south, filling the polar lakes with rain but mostly leaving the equator out to dry.
As for whether the spring showers are good news for the possibility life on Titan, Turtle and Tokano are agnostic.
‚ÄúThere‚Äôs no liquid water involved in any of the processes we‚Äôre describing here, so life as we know it can‚Äôt exist,‚ÄĚ Turtle said. ‚ÄúBut there‚Äôs clearly so much scope for prebiotic chemistry on Titan‚Ä¶. Understanding Titan better in general helps us to understand what the possibilities are.‚ÄĚ
Images: 1) NASA/JPL/Space Science Institute. 2) P. Huey/Science AAAS
Citation:‚ÄúRapid and Extensive Surface Changes Near Titan‚Äôs Equator: Evidence of April Showers.‚ÄĚ E.P. Turtle, J.E. Perry, A.G. Hayes, R.D. Lorenz, J.W. Barnes, A.S. McEwen, R.A. West, A.D. Del Genio, J.M. Barbara, J.I. Lunine, E.L. Schaller, T.L. Ray, R.M.C. Lopes, E.R. Stofan. Science, Vol 331, March 18, 2011. DOI: 10.1126/science.1201063.
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