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Mar 23 11 2:01 AM
When it comes to determining exactly where in the solar system life began, things have never been so up in the air. Scientists over the past decade have suggested deep-sea hydrothermal vents, underground aquifers, partially frozen lakes and even comets as locations for the origin of life.
Now an experiment that simulates chemical reactions in the atmosphere of Titan, Saturn’s haze-shrouded moon, adds a new location to the list of unexpected places where life could have begun — in the sky.
The study used radio waves as an energy source, simulating the action of ultraviolet radiation from the sun that strikes the top of Titan’s thick atmosphere and breaks apart molecules such as methane and molecular nitrogen. The experiment is the first to produce amino acids and the nucleotide bases that make up DNA and RNA — the basic ingredients of life — without the need for liquid water, says Sarah Hörst of the University of Arizona in Tucson. She and her colleagues presented the findings in Pasadena, Calif., October 7 at the annual meeting of the American Astronomical Society’s Division for Planetary Sciences.
The results suggest that Titan’s upper atmosphere, about 1,000 kilometers above the frigid moon’s surface, produces compounds capable of supporting life. And because planetary scientists believe that Titan represents a frozen snapshot of the early Earth, the study also indicates that terrestrial life might have formed within a primordial haze high above the planet rather than in a primordial soup on the surface, Hörst says.
Planetary scientist Jonathan Lunine of the University of Arizona, who was not part of the study, notes that the compounds found in the experiment “are relatively simple precursor molecules to life, and so there are a lot of additional steps between such molecules and life itself, most of which will likely require a liquid, such as water or methane.” However, he adds, everything that forms high in Titan’s atmosphere ends up in the moon’s lakes and seas of methane.
The study is provocative, Lunine says, because the Cassini spacecraft detected heavy ions in Titan’s atmosphere, but they were too massive for the craft’s instruments to identify. Amino acids were among the potential candidates for those heavy compounds, which were found in the terrestrial simulation.
To confirm that amino acids and nucleotide bases are actually produced in Titan’s atmosphere will require an orbiter that can carry instruments 100 to 200 kilometers deeper than Cassini does into Titan’s haze layer, Lunine says.*
_______________________________________________*: THIS IS KNOWN ALREADY,please! (CBK)
Earthlings might be scrambling to find liquid hydrocarbons buried in our planet, but Saturn’s moon Titan has plenty to spare.
Scientists say that a dark, smooth surface feature spotted on the moon last year is definitely a lake filled primarily with liquid ethane, a simple hydrocarbon.
"This is the first observation that really pins down that Titan has a surface lake filled with liquid," said the paper’s lead author, University of Arizona professor Robert Brown.
The new observations affirm that Titan is one of the likeliest places to look for life in our solar system. Some astrobiologists have speculated that life could develop in the moon’s hydrocarbon lakes, although it would have to be substantially different from known life on Earth, which requires liquid water.
Mixed in solution with the ethane, the lake is also believed to contain nitrogen, methane, and a variety of other simple hydrocarbons.
The Cassini-Huygens probe determined the chemical composition of the liquid by the way it reflected light, a technique known as spectrometry that has provided most of our knowledge about other planets’ atmospheric compositions.
"It was hard for us to accept the fact that the feature was so black when we first saw it," Brown said. "More than 99.9percent of the light that reaches the lake never gets out again. For it to be that dark, the surface has to be extremely quiescent, mirror smooth. No naturally produced solid could be that smooth."
Further, the scientists saw the specific absorption signature of ethane, which absorbs light at exactly 2-micron wavelengths.
These kinds of measurements are made more difficult by the hydrocarbon haze that engulfs the moon, making it hard to actually see the Titanic ground. Cassini scientists have to take advantage of narrow observation windows. One of these occurred in December 2007, which allowed them to catch this view of the lake, Ontario Lacus. At 7,800 square miles, it’s slightly larger than the Earthbound Lake Ontario
Ethane is the byproduct of a solar-energy-induced reaction that transforms atmospheric methane, aka natural gas. Scientists believe ultrafine particles of ethane fall from the atmosphere to the surface and fill the lake.
Here on earth, ethane is used to create ethylene, which is used as an all-purpose chemical precursor and is the world’s most-produced organic compound.
Brown and his team will publish their results in the July 31 issue of the journal Nature.
Image: Courtesy NASA. Ontario Lacus, which translates roughly to "Bigfoot track on Saturnian moon."
Mar 23 11 2:28 AM
Cassini’s view of Saturn shortly after the spring equinox in August, 2009. NASA/JPL/SSI
A crack in one of Saturn’s rings could be held open by the planet’s largest moon, Titan. A new analysis of data from the Cassini orbiter shows that Titan’s gravity lifts part of the ring in a rotating tidal wave almost two miles high.
NASA/JPL/Cornell“It’s a little bit like a tsunami propagating away from an earthquake fault,” said planetary scientist Phillip Nicholson of Cornell University in a press briefing Oct. 4. Nicholson presented a new model explaining the ring gap at the American Astronomical Society’s Division for Planetary Sciences meeting in Pasadena, California.
Saturn’s rings are riddled with gaps, many of which are held open by small moons. But in the last five years, since Cassini discovered the moon Daphnis, no new moons have shown up in the other known fissures.
“It’s become an increasing problem, as to what determines where these gaps are in the rings and what keeps the gaps open,” Nicholson said.
One such gap has been a mystery since the Voyager 1 spacecraft flew by Saturn in the 1980s. Using radio observations, Voyager detected what looked like a 9-mile-wide gap in the middle of Saturn’s C ring. Just outside the gap, astronomers saw a wave-like structure circling the ring, which they interpreted as an extra-clumpy region pushing through the ring’s flat disk.
But Cassini found the gap to be much narrower, only about a mile and a half wide. Even weirder, the gap seemed to disappear about half the time.
Both puzzles can be resolved by thinking of the ring in three dimensions, Nicholson says. Last year, the angle of sunlight during Saturn’s spring equinox revealed that many of Saturn’s rings have mountains.
“Mostly the rings are very flat. It’s the most two-dimensional structure we know in the universe,” Nicholson said. “But there are exceptions to every rule, and there are exceptions to the rule that Saturn’s rings are flat everywhere.”
The new model suggests the actual gap in the ring is only about a third of a mile wide, but part of the ring rises 2 miles in the air. The crack looked wider to Voyager than to Cassini because of the angles the spacecraft were observing from.
“In hindsight, what looked like a 15-kilometer-wide gap actually was this gap with a vertical displacement of about 3 kilometers (1.8 miles), projected and seen almost edge-on,” Nicholson said. “If we assume this was vertical and not horizontal and do the projection, it fits perfectly with this model, better than you have any right to expect.”
The ring’s corrugation comes from a gravitational relationship with Titan, whose orbit around Saturn falls at a slight angle to the ring plane. At a certain point in its orbit, Titan yanks the ring particles upward, starting a wave that travels around the ring.
“The whole pattern rotates around at the same rate as the satellite Titan orbits Saturn, once every 16 days,” Nicholson said. The wave rolling along under Cassini occasionally blocked the spacecraft’s view. “That accounts for the fact that the gap seems to come and go,” he added.
This sort of wave could explain some of the other gaps in Saturn’s rings that are not held open by moons, although it could also be unique to Titan and the C ring, Nicholson said.
“This and some other work suggests there might not be one explanation for gaps, there may be three or four or even more different dynamical circumstances that can give rise to these gaps.”
The insights gleaned from Saturn’s rings can be applied to disks all over the galaxy, including disks around stars that will eventually coalesce into planets, added Linda Spilker, Cassini deputy project scientist at the Jet Propulsion Laboratory.
“Saturn really is a wonderful, natural lab for understanding how the protoplanetary nebula might have evolved,” she said.
Video: Moon Builds Snowballs in Saturn Ring
Mar 23 11 2:31 AM
The fortuitous lighting of Saturn’s equinox has revealed the planet’s famously smooth, flat rings are actually corrugated.
During the days immediately after the August 11 equinox, the sun’s rays struck the rings at very low angles, bringing their topography into high-relief.
For scientists studying the rings, the event happening once every 15 years provided an unprecedentedly dimensional view of the rings.
They were thought to be about 30 feet thick — and they are, generally speaking — but the Cassini spacecraft has revealed regions that are nearly two miles high.
“Like the seas of Earth, this wide icy expanse has settled into a mathematically precise cast that, here and there, froths and churns, not by wind but by the convulsive forces of Saturnian moons,” Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, wrote in her Captain’s Log. “This famous adornment, impressed deep in the human mind for four centuries as a pure, two-dimensional form, has now, as if by trickery, sprung into the third dimension.”
There are several different types of clumps and corrugations and walls within the rings. Scientists have different theories about how the structures might form. Some of them, they know, are caused by Saturn’s moons.
“It turns out that as the orbits of the moons are a little inclined relative to the ring plane, they pull the particles out of the plane,” said Linda Spilker, Cassini deputy project scientist at the Jet Propulsion Laboratory in Pasadena, California.
In the picture above, the ring mountains can be seen at the upper right casting a shadow on the gray ring to the right. They were pulled up out of the ring plane by the moon Daphnis.
Other structures seen in the rings are more mysterious. Corrugations across the C and D rings could have been caused by a collision with some kind of space object, but Spilker said the Cassini team isn’t sure about that.
In general, the scientists were surprised by the amount of height variation within the rings, most of which they were only able to see because of the good timing of the mission.
“It was very lucky that we had Cassini at the rings at the right time,” Spilker said.
The image at the top of the post shows Saturn a day and a half after the equinox. It has been enhanced to increase the drama of the view, and Porco provided a wonderfully detailed explanation of how the image was created.
“To improve their visibility, the dark (right) half of the rings has been brightened relative to the brighter (left) half by a factor of three, and then the whole ring system has been brightened by a factor of 20 relative to the planet,” Porco wrote. “So the dark half of the rings is 60 times brighter, and the bright half 20 times brighter, than they would have appeared if the entire system, planet included, could have been captured in a single image.”
Images: NASA/JPL/Space Science Institute.
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Mar 23 11 2:49 AM
If we ever do find extraterrestrial life in the solar system, it’s probably much more likely to look like a few cells than a walking-and-talking green man. Nonetheless, finding any kind of life beyond Earth would be extraordinary. Here are our best hopes:
1. EnceladusThe sixth-largest moon of Saturn has been called the most promising bet for life thanks to its welcoming temperature and the likely presence of water and simple organic molecules. The surface of the icy moon is thought to be about 99 percent water ice, with a good chance of liquid water beneath. Observations from the Cassini probe’s 2005 flyby of Enceladus suggest the presence of carbon, hydrogen, nitrogen and oxygen — organic molecules thought to be necessary to develop life. And the moon seems to have a boiling core of molten rock that could heat the world to the toasty temperatures needed to give rise to life. (Image: Cassini Imaging Team, SSI, JPL, ESA, NASA)
2. EuropaJupiter’s moon Europa also seems a possible stomping ground for E.T. due to its potential water and volcanic activity. Though the surface seems to be frozen, many suspect that buried underneath is an ocean of liquid water. Volcanic activity on the moon could provide life-supporting heat, as well as important chemicals needed by living organisms. Microbial life could potentially survive near hydrothermal vents on Europa, as it does on Earth.(Image: Galileo Project, JPL, NASA; reprocessed by Ted Stryk)
3. MarsAs far as planets go, by far the front-runner for life is our next-door neighbor, Mars. The red planet is the most Earth-like of solar system planets, with a comparatively similar size and temperature range as our own planet. Large bodies of water ice lie on Mars’ poles, and there’s a reasonable chance of liquid water beneath the surface. The puny atmosphere on the planet is not strong enough to shield the planet against lethal solar radiation, though microbes could potentially exist beneath the surface. Evidence also suggests that Mars may have been even more habitable in the past. Geologic features imply that liquid water once flowed across the surface, and volcanic activity, now dead, once flourished, recycling chemicals and minerals between the surface and the interior. (Image: NASA and the Hubble Heritage Team (STScI/AURA))
4. TitanSaturn’s largest moon looks suspiciously like it might have hosted life, because its thick atmosphere is rich in compounds that often mark the presence of living organisms. For instance, Titan’s air is filled with methane, which is usually destroyed by sunlight. On Earth, life constantly replenishes methane, so it might similarly be responsible for the methane on Titan. Titan is rather cold, however, and if liquid water exists, it must be deep beneath the frozen surface. (Image: NASA)
5. Io Jupiter’s moon Io is one of the few solar system moons to support an atmosphere, and it contains complex chemicals promising for life. Volcanism on the moon also makes it warmer than many others — another good sign. Io is still a long shot, though, because its location inside Jupiter’s magnetic field means it is constantly being pelted with lethal radiation. Its violent surface also seems inhospitable, with temperatures often too cold to support life, as well as molten hot spots that are equally deadly.(Image: The Galileo Project, JPL, NASA)
Mar 23 11 2:54 AM
The Huygens probe has captured an image of what may be the first drop of liquid ever observed on an extraterrestrial surface.
The photo is evidence that liquids may exist on the surface of other planets and moons, not just frozen lakes. And liquid is more likely habitat for extraterrestrial life.
Among the pictures snapped by the Huygens probe after landing on Saturn’s moon Titan in 2005, one appears to show a dewdrop made of methane that briefly formed on the edge of the probe itself (indicated by arrow at bottom of image on right). Scientists think heat from the probe caused humid air to rise and condense on the cold edge of the craft.
Though Huygens may have helped produce it, the methane drop is still the first liquid directly detected at a surface anywhere beyond Earth.
Like Earth, Titan has clouds, lakes and river channels, and it may be the only other place in the solar system where liquid evaporates from the surface and returns as rain. "Aside from Earth, it’s the most exciting world there is," said lead author Erich Karkoschka of the University of Arizona in Tucson.
The Cassini space probe, which took data from above the moon after separating from the Huygens lander, detected what scientists believe are lakes of liquid methane on Titan’s surface. Microbes that eat methane thrive on Earth, and scientists think pools of methane could be comfortable homes for similar organisms on Titan.
Because Titan’s current atmosphere is a lot like the early Earth’s, the lakes could be a lab for studying the origins and early evolution of life.
Astronomers have speculated since they found methane in the atmosphere in 1983 about whether the moon’s methane rain falls in violent thunderstorms, light drizzles or some other form. So far, no one has caught it on camera.
The hundreds of images snapped by Huygens, from the time it hit the atmosphere until its power ran out an hour after it landed, revealed only faint, wispy clouds that looked nothing like rain clouds, Karkoschka said.
None of the images showed evidence that it had rained during the previous few years, according to an analysis to be published in the journal Icarus. And some images suggested that Titan’s lower atmosphere was full of small dust particles, which would have been cleared out by rain.
But the scientists noticed light splotches in some of the pictures that hadn’t been there moments before. Some of them had spots that initially looked like raindrops because of their uniform size and smooth edges, but analysis showed they were most likely electronic imprints created by cosmic rays.
However, Karkoschka said, "One of those spots was so big that it really cannot be a cosmic ray." He concluded that it was a real, short-lived dewdrop, so close to the camera that it must have condensed on a cold metal shield designed to protect the camera lens from direct sunlight.
Robert West, a planetary scientist at the Jet Propulsion Lab in Pasadena, California, thinks the dewdrop is "a cute observation," but he’s more interested in the lack of rainfall. "There are reports in the literature that concluded there is a drizzle going on near the surface," he said. "The fact that Huygens didn’t find anything is significant."
— Lisa Grossman for Wired.com
May 9 11 9:06 AM
Titan holds yet more secrets beneath its haze. Credit: NASA / JPL / SSI
Saturn's moon Titan just keeps throwing surprises at us. A multi-layered atmosphere thicker than our own? Check. A hydrologic cycle that relies on methane as the operating liquid? Check. Rivers, streams and lakes filled with this same liquid? Check, check and check. And now, scientists are suspecting that Titan may have yet another surprise: a subsurface ocean. Observations of Titan’s rotation and orbit, carried out by researchers at the Royal Observatory of Belgium using Cassini data, point at an unusual rotational inertia; that is, its resistance to changes in its motion, also known as moment of inertia or angular mass. Basically Titan moves in a way that is not indicative of a solid body of its previously assumed density and mass. Rather, its motion – both around its own axis and in its tidally-locked orbit around Saturn – are more in line with an object that isn’t uniformly solid.According to the math, Titan may very well be filled with liquid!Or, at least, have a liquid layer of considerable depth beneath its surface. How far below the surface, how deep and exactly what kind of liquid are all speculative at this point…it’s suggested that it may be a subsurface ocean of yet more methane. This would help answer the question of where Titan gets all of its methane in the first place; methane, – a.k.a. natural gas – is a compound that breaks down quickly in sunlight. In fact, the high-level haze that surrounds the moon like a wispy blue shell is made up of this broken-down methane. So if this stuff is raining down onto the surface in giant, frigid drops and filling streams and lakes, but is still being broken down by ultraviolet light from the Sun to enshroud the entire moon (Titan is BIG, remember…at 5,150 km – 3,200 miles – wide, it’s over a third the size of Earth!) then there has to be somewhere that this methane is coming from.If these calculations are right, it may be coming from underground. "We propose a new Cassini state model for Titan in which we assume the presence of a liquid water ocean beneath an ice shell… with the new model, we find a closer agreement between the moment of inertia and the rotation state than for the solid case, strengthening the possibility that Titan has a subsurface ocean." said Rose-Marie Baland et al. Of course in order for this hypothesis to be proven many more numbers are going to have to be crunched and more data reviewed. And more possibilities considered, too; Titan’s orbital irregularities may in fact be the result of external forces, such as a close pass by a comet or other large body. Still, there’s something to be investigated here and you can bet there’ll be no shortage of attention on a problem as intriguing as this!Titan may soon be joining the short list of moons speculated to possess subsurface oceans, alongside Jupiter’s Europa and Ganymede and sister Saturnian satellite Enceladus…and who knows how many others?
More information: You can download the full report here.
Source: Universe Today
Source: Astrobio.net (news : web)
This artist's illustration shows the likely interior structure of Saturn's moon Titan. The cool and sluggish interior failed to separate into completely differentiated layers of ice and rock. In addition to the hazy surface of Titan (yellow), the layers in the cutaway show an ice layer starting near the surface (light gray), an internal ocean (blue), another layer of ice (light gray) and the mix of rock and ice in the interior (dark gray). In the background are the Cassini spacecraft and Saturn, not to scale. Credit: NASA/JPL
Oddities in the rotation of Saturn's largest moon Titan might add to growing evidence that it harbors an underground ocean, researchers suggest.
The surface of Titan has some of the largest bodies of liquid ever seen. However, these lakes are composed of hydrocarbons. Scientists believe that oceans of liquid water and ammonia may be contained beneath the surface of the moon. Credit: NASA/JPL"We found it very exciting to use some measurements that seem in contradiction and to try to reconcile them," Baland said. "It was like putting together pieces of a puzzle." Still, the case for Titan having an underground ocean is not closed yet. Its orbit and rotation might also be explained by a recent disturbance, such as a collision with a comet or asteroid."Our analysis strengthens the possibility that Titan has a subsurface ocean, but it does not prove it undoubtedly," Baland told Astrobiology Magazine. "So there is still work to do." Since life as we know it needs liquid water, if Titan does have a subsurface water ocean that may increase the chances the moon could harbor alien life.
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