Artist’s rendering of AVIATR flying on Titan.
Saturn’s moon Titan is a lot like Earth: it has rain, seasons, volcanoes, and maybe even life. Well, it’s not exactly like Earth: the rain is liquid methane, the volcanoes spew ice, and any life would be based on methane. But still, it’s an interesting and relatively Earth-like place, considering the other planets and moons in our solar system. And University of Idaho physicist Jason Barnes says he has a perfect way to explore this moon: with a flying drone.
Why use a flying machine rather than the rovers that worked so well on Mars? With 1/7 the gravity but 4 times the atmospheric density of Earth, flying through Titan is 28 times easier than on our own planet. In fact, it’s the easiest place to fly in our entire solar system. Drones on Titan can be heavier while requiring less fuel. With these facts in hand, University of Idaho physicist Jason Barnes has proposed AVIATR, otherwise known as the Aerial Vehicle for In-situ and Airborne Titan Reconnaissance.
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What’s the News: NASA’s considering launching a boat from Earth, hurling it 746 million miles through space, and plopping it onto one of the minus-290 degrees Fahrenheit methane oceans of Titan. This mission to Saturn’s largest moon would the first of its kind to probe an alien ocean and—depending on the weather conditions—could be the first spacecraft to witness extraterrestrial rain. If the proposed mission beats out two other finalists, it could launch within the next five years. “Titan is an endpoint [in] exploring … the limits to life in our solar system,” project leader Ellen Stofan told New Scientist. “We’re going to be looking for patterns in abundances of compounds to look for evidence for more complex or interesting reactions.”
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What’s the News: Astronomers have known for many years that Saturn’s moon Titan sports lakes of liquid methane. And in the past couple years, scientists have suggested that it also has an underground ocean composed of water and ammonia. Now, based on past observations by NASA’s Cassini spacecraft, astronomers are saying that Titan’s rotation indeed points to an underground sea—and where there’s water, there may also be life. “Our analysis strengthens the possibility that Titan has a subsurface ocean, but it does not prove it undoubtedly,” researcher Rose-Marie Baland told Astrobiology Magazine. “So there is still work to do.”
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What’s the News: Images sent back from NASA’s Cassini spacecraft depict storm clouds and methane rain puddles, the first solid evidence of modern rainfall on Titan, Saturn’s largest moon. “We’re pretty confident that it has just rained on Titan,” lead author Elizabeth Turtle, from Johns Hopkins University Applied Physics Laboratory, told Wired. Astronomers have previous evidence of sulfuric-acid precipitation on Venus, but it doesn’t count as rainfall because it never reaches the surface.
What’s the Olds:
Not So Fast: Don’t read too much into these showers: Methane rain doesn’t mean life. The search continues.
Reference: “Rapid and Extensive Surface Changes Near Titan’s Equator: Evidence of April Showers.” 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
Image: NASA/JPL/Space Science Institute
Saturn’s moon Titan has lakes on its surface and a thick atmosphere, but there’s one more way this cold, distant world is like the Earth: It appears to have volcanoes—though they’re a little chillier than Eyjafjallajökull.
Scientists have long suspected and presented some evidence that Titan could have these features, and this week at the American Geophysical Union meet-up, researchers presented a finding from the Cassini spacecraft that they say is the best evidence yet of a Titanic volcano.
“We finally have some proof that Titan is an active world,” said geophysicist Randolph Kirk of the U.S. Geological Survey, who presented the findings. [NPR]
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It’s just a lab experiment, but University of Arizona researcher Sarah Horst says that her team’s re-creation of the atmosphere on Saturn’s moon Titan showed that atmospheric reactions could produce some of life’s basic ingredients, and do it without the presence of liquid water.
Titan, which is larger than Mercury, boasts a thick atmosphere of mostly nitrogen with dashes of methane, carbon monoxide, and other trace ingredients (At -290 degrees Fahrenheit, Titan is a tad too frigid for liquid water). Horst brewed up an approximation of that mixture. She and her colleagues then blasted it with radio-frequency radiation, a lab stand-in for ultraviolet radiation from the sun.
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Carbonated oceans, moons torn apart, ring tsunamis—there’s a flurry of cool news about Saturn coming out of the American Astronomical Society’s Division for Planetary Science meeting in Pasadena, California.
The fizzy ocean of Enceladus
Saturn’s moon Enceladus is one of the prime candidates for some kind of life elsewhere in the solar system, thanks the the possibility that a large subsurface ocean feeds the plumes of ice and vapor that the Cassini spacecraft has spied blasting forth from the moon. At the AAS meeting in California, Cassini scientists Dennis Matson proposed something new about this extraterrestrial ocean: It could be carbonated.
Noncarbonated seawater circulating from the moon’s solid core to the surface would stall rather than seep though cracks in the ice because seawater is denser than the icy carapace. If the seawater were fizzy, however, gas bubbles would form in the liquid, reducing the ocean’s density. Once the seawater became less dense than the ice, the water could rise to within 10 to 15 meters of the frigid surface. That’s close enough to fill chambers in the icy crust with water that feeds the south polar plumes. [Science News]
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Lake Ontario has some key differences compared to her equally-sized sister lake, Ontario Lacus: The Great Lake has water; Ontario Lacus has methane, ethane, and propane. The Great Lake invites sunbathers; Lacus’ beaches, almost ten times further from the sun, are icy cold. The Great Lake is located on Earth; Lacus on Saturn’s largest moon, Titan. Despite all these distinctions, new research points to an important similarity: liquid levels in both lakes change with the seasons.
From June 2005 to July 2009, the Ontario Lacus shoreline has receded by about 6 miles, Alexander G. Hayes and his coauthors report in two papers submitted to Icarus and the Journal of Geophysical Research. Looking at other lakes in Titan’s southern hemisphere, it seems they are dropping in depth by about three feet per year.
Despite its shoreline’s rapid retreat, there is little worry that Ontario Lacus and other Titan lakes will disappear forever. Scientists expect that the evaporation is just part of a cycle of evaporation and condensation, that changes with the seasons. The four years of observation, carried out by NASA’s Cassini spacecraft, represents only the period from about mid-summer to fall, since a Titan year lasts 29.5 Earth years.
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If there were life on the Saturnian moon of Titan, the thinking goes, it would have to inhabit pools of methane or ethane at a cool -300 degrees Fahrenheit, and without the aid of water. While scientists don’t know just what that life would look like, they can predict what effects such tiny microbes would have on Titan’s atmosphere. That’s why researchers from the Cassini mission are excited now: They’ve found signatures that match those expectations. It’s far from proof of life on Titan, but it leaves the door wide open to the possibility.
In 2005, NASA’s Chris McKay put forth a possible scenario for life there: Critters could breathe the hydrogen gas that’s abundant on Titan, and consume a hydrocarbon called acetylene for energy. The first of two studies out recently, published in the journal Icarus, found that something—maybe life, but maybe something else—is using up the hydrogen that descends from Titan’s atmosphere to its surface:
“It’s as if you have a hose and you’re squirting hydrogen onto the ground, but it’s disappearing,” says Darrell Strobel, a Cassini interdisciplinary scientist based at Johns Hopkins University in Baltimore, Md., who authored a paper published in the journal Icarus [Popular Science].
Erring on the side of caution, the scientists suggest that life is but one explanation for this chemical oddity. Perhaps some unknown mineral on Titan acts as a catalyst to speed up the reaction of hydrogen and carbon to form methane, and that’s what accounts for the vanishing hydrogen. (Normally, the two wouldn’t combine fast enough under the cold conditions on Titan to account for the anomaly.) That would be pretty cool, though not as much of a jolt as Titanic life.
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Extremophiles microbes: They’re tougher than you. Scientists have found microorganisms living in the ultra-dry Atacama desert, Antarctica, volcanic hot springs, and now, lakes of asphalt.
Trinidad, the larger island of the Caribbean duo Trinidad and Tobago, is home to Pitch Lake. This 100-acre pool of hot liquid asphalt is the largest of its kind on our planet, but microbiologist Steven Hallam thought it could tell us something about another world: the Saturnian moon of Titan. If anything could live in the toxic stew of Lake Pitch, he thought, perhaps there’s hope for the hydrocarbon lakes and rivers of that distant moon. He found that the earthly lake teems with life. “Water is scarce in the lake and certainly below the levels normally thought of as a threshold for life to exist,” he says. “Yet on average, each gram of ‘goo’ in the lake contains tens of millions of living cells” [Australian Broadcasting Corporation].
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With its thick atmosphere, chemical makeup, and an atmospheric pressure not too far from Earth’s, Titan is one of the most likely candidates for finding life elsewhere in our solar system. But at a temperature close to -300 degrees Fahrenheit, the surface of this Saturnian moon in anything but what we humans would call hospitable. Since this frigid place is far too cold for liquid water, any life there would need an alternative survival method. A new study published in Astrophysical Journal Letters suggests that the simple hydrocarbon acetylene, proposed as a possible energy source for life on Titan, could be much more abundant than scientists previously thought.
Titan has previously been shown to be dotted with lakes of liquid hydrocarbons, primarily methane and ethane. An estimate made in 1989 suggested bodies of liquid hydrocarbons on Titan would contain a few parts in 10,000 of acetylene. But an updated estimate based on data from the Cassini-Huygens mission to Saturn now suggests the lakes contain much more food for any hungry alien life-forms that might be present [New Scientist]. Lead researcher Daniel Cordier says the acetylene abundance could be as high as one part in 100, or 1 percent, of the surface lakes on Titan.
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While it may not be a colorful extravaganza like autumn in New England, astronomers have been awaiting the change of seasons on Saturn’s moon Titan with considerable anticipation. The Cassini space probe has been monitoring Titan since 2004, but as the moon’s year lasts 30 Earth years, it has only ever seen one season. The equinox marking the end of summer in the south will come this August. “This is our first opportunity to look at seasonal change,” says [researcher] Bonnie Buratti…. “And it’s not as simple as it might have been” [New Scientist].
Indeed, Cassini‘s observations have revealed some surprises in Titan’s atmosphere. The moon currently has clouds of methane (which sometimes produce methane rain showers) in its southern hemisphere. These southern clouds are thought to be caused by convection in Titan’s atmosphere, driven by the heat of the sun [New Scientist]. But astronomers’ models of Titan predicted that the southern clouds would have disappeared by now as the moon approaches its equinox. Says study coauthor Sebastien Rodriguez: “Titan’s clouds don’t move with the seasons exactly as we expected…. 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” [UPI].
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Saturn‘s moon Titan is already an object of fascination to astronomers: The moon has seasonal weather patterns, a thick atmosphere, and lakes of liquid methane on its surface, and some scientists think it’s one of the likeliest spots to find extraterrestrial life in our solar system. Now, researchers have found new evidence that the moon has cryovolcanoes, which, in the cold of the outer Solar System, would spew a slurry of ice and liquid hydrocarbons, instead of lava. “It’s as if it’s a sort of constant bubbling cauldron that occasionally explodes big time,” says Robert Nelson, a Cassini team scientist [Nature News].
The still-controversial theory regards an area of Titan called Hotei Arcus, which appears to fluctuate in brightness on timescales of several months…. The cryovolcanism idea was bolstered in 2008, when observations of Hotei Arcus by a radar instrument aboard NASA’s Cassini probe revealed structures that resembled lava flows [New Scientist]. The new findings, discussed at this week’s Lunar and Planetary Science Conference, are based on radar images taken by Cassini on recent flybys of the moon (radar is required to penetrate Titan’s thick methane atmosphere). Overlapping images were used to create a topographical map of Hotei Arcus; the map shows several lobe-like formations, more than 300 feet high, which researchers say resemble the oozing of a viscous, lava-like material.
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Imagine a world where the average daytime temperature is -179°C, and torrential rains of liquid methane fall from the skies, forming vast but shallow pools that cover an area larger than the Great Lakes [ScienceNOW Daily News].
That’s the vision of the Saturnian moon Titan provided by the NASA spacecraft Cassini, which has been exploring Saturn and its satellites since 2004. In the latest findings, Cassini scientists have determined that Titan has seasonal weather patterns in which fierce storms fill up the methane lakes. “We see clouds that behave very much as clouds on Earth, and we see evidence of flooding on the surface, just as a lot of people in the [U.S.] Midwest saw last year” [National Geographic News], researcher Elizabeth Turtle said.
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Which celestial bodies are more likely to host extraterrestrial life: Saturn’s hazy moon Titan and water-spewing moon Enceladus, or Jupiter’s icy moons Europa and Ganymede, which may have liquid oceans beneath their frozen crusts? That’s the difficult question facing NASA and the European Space Agency (ESA) as they try to decide where to send the next planetary probe. By the end of this month, agency officials plan to pick a destination for a massive mission, costing nearly US$4 billion, to be launched around 2020 for the distant reaches of the Solar System. The battle pits Titan, which recent discoveries have made the cool new kid on the block, against Jupiter’s moon Europa, which has long sat atop community wish lists [Nature News].
In advance of that decision, the space agencies have released details of the dueling proposals. The potential Saturn mission would follow up the remarkable discoveries made by the Nasa/Esa Cassini-Huygens mission which continues to operate at the ringed planet…. Cassini has sent back data that indicates Titan is akin to a primitive – albeit frozen – Earth. It has a thick atmosphere and is rich in organic (carbon-rich) molecules [BBC News]. The plan calls for an orbiter that would release a hot air balloon to drift in Titan’s hazy atmosphere and would drop a lander to the surface, where it could float on one of moon’s lakes of liquid ethane and methane. The orbiter would also dip into the atmosphere of Enceladus, which has fired imaginations with the revelation that it has geysers that spew jets of icy water into space.
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