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: 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
A new sight appeared on Saturn earlier this month: A massive, swirling storm with a tail that cuts across the gas giant. Amateur astronomer Anthony Wesley, who was the first to spot the Earth-sized scar on Jupiter last summer, took the first pictures of this storm. And then on Christmas Eve the Cassini spacecraft beamed home its own ravishing images.
From Phil Plait:
The spacecraft took images of the planet on December 24th, returning — as usual — jaw-dropping pictures of Saturn showing the storm. This image, taken with a blue filter, shows the storm clearly. The main spot is huge, about 6,000 km (3600 miles) across — half the size of Earth! Including the tail streaming off to the right, the whole system is over 60,000 km (36,000 miles) long.
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There’s an added bonus in these images: the shadow of the rings on the planet’s clouds is obvious, but the rings are nearly invisible! You can just make out the rings as a thin line going horizontally across Saturn in the first image. These pictures were snapped when Cassini was almost directly above the rings, which are so thin they vanish when seen edge-on. Actually, that works out well as otherwise they might interfere with the view of the storm in these shots.
For more details, check out the rest of Phil’s post at Bad Astronomy.
Related Content:
80beats: By Demolishing a Moon, Saturn May Have Created Its Rings
80beats: Mysterious Smash on Jupiter Leaves an Earth-Sized Scar
Bad Astronomy: Saturn rages from a billion kilometers away
Image: NASA
Saturn and its moons may owe their distinctive looks to a legacy of destruction.
First, the magnificent rings of the sixth planet: Although astronomers have gazed at the rings for centuries, experts are still debating exactly how these loops formed. Now a new study in the journal Nature proposes that the rings are the leftovers of a large moon that was torn asunder when Saturn’s gravity reeled it in four and a half billion years ago. Lead researcher Robin Canup says this theory explains both how the rings got there, and why they’re made of nearly solid ice.
In the new study, Canup calculated that a moon the size of Titan — Saturn’s largest at some 5,000 kilometers across — would begin to separate into layers as it migrated inward. Saturn’s tidal pull would cause much of the moon’s ice to melt and then refreeze as an outer mantle. As the moon spiraled into the planet, Canup’s calculations show, the icy layer would be stripped off to form the rings. [Science News]
That layered removal is the key to Canup’s explanation, which we covered briefly when she first presented the idea at a meeting in October. Other explanations for the rings’ formation include a comet crashing into a moon, or Saturn pulling in a moon and causing it to shatter all at once. Those events would create a cascade of small objects that Saturn’s gravity could have coalesced into rings, but it would seem that they would have created much rockier rings. In reality, Saturn’s are 95 percent ice.
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When the news comes from Saturn’s moons, the source is typically Titan—with its hazy atmosphere and frigid surface lakes of methane—or Enceladus—with its plumes of water ice. Last week, however, word came that Rhea, the second-largest Saturnian satellite, has some surprises of its own.
In Friday’s edition of Science, a study by Ben Teolis and colleagues confirmed that during a pass of the moon in March, when the ever-reliable Cassini spacecraft cruised over Rhea’s pole at an altitude of just 60 miles, it directly sampled tiny amounts of oxygen and carbon dioxide there.
“This really is the first time that we’ve seen oxygen directly in the atmosphere of another world,” said Andrew Coates, at UCL’s Mullard Space Science Laboratory, a co-author of the study. [The Guardian]
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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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Chalk up one more mind-blowingly beautiful Saturn image to the Cassini spacecraft. The fruitful mission beamed home this stunner as part of a video of the auroras on the sixth planet.
Auroras on Saturn form like those on Earth, when charged particles in the solar wind stream down the planet’s magnetic field towards its poles, where they excite gas in the upper atmosphere to glow. Some auroras on the ringed planet are also triggered when some of its moons, which are electrically conducting, move through the charged gas surrounding Saturn. [New Scientist]
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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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They’re new, they’re small, and they didn’t make sense.
That’s what could be said for five of the littlest members of Saturn’s expansive satellite family. The largest of this group, Janus, measures barely more than 100 miles in diameter, but it’s the age of these little moons that’s the odd bit. Their clean, crater-free surfaces help reveal that they’re only 10 million years old, meaning they didn’t form the way the planet’s other moons did—from the accretion disk that formed mighty Saturn itself billions of years ago. This week in Nature, astronomers published evidence to support an explanation for that oddity: Those moons formed from Saturn’s rings.
Like so much new knowledge about the sixth planet and its moons, including Titan and Enceladus, the research team’s findings come from the Cassini mission:
Sailing past Saturn’s outer rings, it found lumps of ice up to 100 metres across, ten times bigger than the rings’ other icy particles. For some researchers, the discovery called to mind another intriguing fact: that the moons and the rings share a composition of the purest ice in the Solar System. “When you put all this together, you had the strange feeling that something is going on in the rings’ outer edge,” says Sébastien Charnoz at Paris Diderot University, who was involved in the latest research [Nature].
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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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When we last covered NASA’s Stardust mission a couple weeks ago, we noted that it was one of those missions that just keeps popping up as new findings from its data makes the news. But Stardust might by outdone by another: Cassini, which continues to reveal new surprises about Saturn and its moons—not to mention sending back beautiful images like this new batch. Today in the journal Science, Cassini researchers review six years of Saturn science (here and here) by the hardy spacecraft.
The first review tackles the planet’s atmosphere and magnetosphere. Before Cassini, scientists thought that the magnetosphere, the shield from the solar wind that forms around a planet, contained nitrogen ions that had come from Saturn’s largest moon, Titan. Cassini showed that wasn’t so, and that wasn’t the only surprise about the magnetosphere: The spacecraft’s observations showed that it is dominated by water, part of which comes from water vapor plumes that shoot out of geysers on the surface of Saturn’s moon Enceladus. “The big news is that Saturn’s space environment is swimming in water,” said Tamas Gombosi, a Cassini scientist [Space.com].
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Water, water everywhere. Another pass of Saturn’s moon Enceladus, made by the Cassini spacecraft last November, shows at least 30 geysers blasting water from the moon’s south pole. That’s 20 more than were previously known at that location. In addition, the most detailed infrared map of one of the south pole’s fissures, where jets emanate, indicates that the surface temperature there might be as high as 200 kelvins (-73º Celsius), or about 20 kelvins warmer than previously estimated [Discovery News]. Cassini drew to within about 1,000 miles of Enceladus to measure this geological feature, which is a fracture–one of the moon’s so-called “tiger stripes”–about a quarter-mile deep officially called Baghdad Sulcus.
While 200 kelvins is still a frigid temperature for we humans, research team member John Spencer said it could make a big difference on Enceladus. “The huge amount of heat pouring out of the tiger stripe fractures may be enough to melt the ice underground,” Spencer said. ”Results like this make Enceladus one of the most exciting places we’ve found in the solar system” [Wired.com].
For more info (and some spectacular photos), check out DISCOVER blogger Phil Plait’s post at Bad Astronomy. And see 80beats’ previous coverage of Enceladus below:
Bad Astronomy: Enceladus Is Erupting!
80beats: Cassini Probe Finds “Ingredients For Life” on Saturn’s Moon Enceladus
80beats: Antifreeze Might Allow For Oceans—And Life—On Enceladus
80beats: Does Enceladus, Saturn’s Geyser-Spouting Moon, Have Liquid Oceans?
80beats: New Evidence of Hospitable Conditions for Life on Saturn’s Moons
80beats: Geysers From Saturn’s Moon May Indicate Liquid Lakes, and a Chance for Life
80beats: Cassini Spacecraft Snaps Pictures of Saturn’s Geyser-Spouting Moon
Image: NASA/JPL/GSFC/SWRI/SSI
Astronomers have found an enormous and diffuse new ring of Saturn that lies far, far beyond the rest of the planet’s famous circlets. Researchers say the new ring is comprised of debris ejected from Saturn’s outlying moon Phoebe during impact. The new discovery also solves a puzzle regarding the curious two-faced appearance of Saturn’s moon Iapetus, whose leading hemisphere is much darker than its trailing side [New Scientist].
The ring, which has claimed the title of largest known ring in the solar system, starts about 3.7 million miles from Saturn and extends outward another 7.4 million miles. Its diameter is equivalent to 300 Saturns lined up side to side. And its entire volume can hold one billion Earths…. “This is one supersized ring” [CNN], says Anne Verbiscer, coauthor of the study published in Nature. The ring has the same orbital tilt as the moon Phoebe–both are tilted at a 27 degree angle from Saturn’s main ring plane–which supports the theory that Phoebe’s ejected dust feeds the ring.
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What lies beneath the icy crust of Enceladus? Ever since the NASA space probe Cassini snapped pictures of the Saturnian moon expelling enormous jets of icy vapor from fissures near its south pole in 2005, planetary scientists have debated whether the evidence points to liquid oceans beneath the moon’s surface. Now, a new chemical analysis of the plume bolsters the oceanic theory, thanks to the detection of a mundane chemical: ammonia. Says study coauthor Jonathan Lunine: “This is the first time Cassini has actually been able to ’smell’ ammonia…. And because ammonia is an antifreeze, it probably ensures that there is liquid water in the interior of Enceladus.” And where there’s water, there could be life [Wired.com].
Last month, another team of researchers also argued for the presence of an ocean when they published their discovery of sodium salts in Saturn’s outer-most ring which is thought to originate from Enceladus’ plume material. “The two studies are complimentary and now, for the first time, we are getting an idea of the full picture of what’s happening on Enceladus,” [Chemistry World], says Frank Postberg, lead author of that earlier study. However, Postberg’s study was contested by another paper that found no traces of sodium vapor around Enceladus, leaving the debate unresolved. Sodium is thought to be an indicator of liquid water because it suggests that salt leached from rocks into the water.
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