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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Saturn’s moon Enceladus got humanity’s attention in 2005 when surprised astronomers detected jets of ice and gas spraying out from the moon’s icy surface, and since then researchers have eagerly investigated the possibility that the jets might emanate from liquid oceans beneath the frozen crust. A moon with liquid water would be of great interest, because it would be more likely to host extraterrestrial microbes. Now, two new studies with somewhat contradictory results have deepened the mystery of what lies beneath Enceladus’s shell of ice.
Both groups of researchers were looking for sodium near Enceladus; one found it, the other didn’t. Sodium is interesting because it indicates that deep under the ice, liquid water has been in contact with rocks, which leach salts [ScienceNOW Daily News]. The dissolved sodium, along with water, would be shot into space in the geysers, and some of the sodium would be trapped in ice crystals as they formed. The first research group found sodium traces in Saturn’s E ring, a wide band of ice particles that is believed to be replenished by Enceladus’s jets. “Those salty grains provide our current best smoking (or steaming) gun pointing to present-day liquid water near the surface of Enceladus” [Wired.com], wrote space scientist John Spencer in an essay accompanying the findings.
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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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The Cassini space probe has detected a tiny moon nestled in one of Saturn’s outermost rings, making it the 61st known Saturnian satellite. The moonlet measures only about one-third of a mile in diameter, but researchers say the diminuitive moon is big enough to be the likely source of the dust that forms the ring, thus solving a mystery.
Cassini spotted the moonlet as a bright streak of light in the second to last ring from Saturn, which is called the G ring. “Before Cassini, the G ring was the only dusty ring that was not clearly associated with a known moon, which made it odd,” said [Cassini scientist] Matthew Hedman…. “The discovery of this moonlet, together with other Cassini data, should help us make sense of this previously mysterious ring” [CNN].
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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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The space probe Cassini, our emissary to Saturn and its fascinating satellites, has made several new discoveries that lend further credence to the idea that microbial life could evolve on the icy moon Enceladus or the moon Titan, with its lakes of methane. During a flyby of Enceladus Cassini snapped pictures of the moon’s surface and the cracks in its icy crust from which jets of water vapor routinely burst upward. The new pictures suggest that the cracks form when the crust splits and spreads apart in a way that is similar to the mid-ocean ridges central to the tectonic system on our own planet. On Earth the spreading of the sea floor is driven by molten rock; Nasa scientists speculate that the liquid beneath the south pole of Enceladus may be water. “Bit by bit, we’re accumulating the evidence that there is liquid water on Enceladus” [Telegraph], said Cassini scientist Carolyn Porco.
Enceladus is already known to have some of the fundamental chemistry required to make and sustain life. Liquid water currently is the major missing ingredient. Dr Porco commented: “We first discovered this region in early 2005 and now it’s nearly four years later, so it’s still kind of brand new; but already there are some of us who really want to go back with a spacecraft that focuses on the south pole of Enceladus and investigates whether or not it is a site of either pre-biotic or biotic processes” [BBC News].
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When NASA’s Cassini spacecraft swooped past Saturn’s moon Enceladus last year, it got a close-up view of the water vapor and ice plumes that stream away from the small moon. After analyzing the data, researchers say the evidence suggests that the material in the plumes originates as liquid water trapped beneath the moon’s icy surface, which increases the possibility that microbial, extraterrestrial life could exist in the lakes. “We think liquid water is necessary for life and there is more evidence that there is liquid water there,” said lead researcher Candice Hansen…. Scientists are aware of only three places where liquid water exists near the surface of a planet or other body – Earth, Jupiter’s moon Europa and now Enceladus [Telegraph].
Researchers identified four distinct jets within the plume where the water vapor appears to be traveling faster than 1,300 miles per hour. Such high speeds imply that the jets are fed by pressurised water vapour that shoots through narrow openings – which act like rocket nozzles – in the moon’s icy surface. The simplest way to generate such pressures is by evaporating a reservoir of liquid water that lies close to the moon’s surface [New Scientist], researchers say.
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Researchers have unveiled the clearest images yet of the massive cyclone that revolves over Saturn’s south pole, and revealed that the southern storm is matched by an equally powerful cyclone at the planet’s north pole. Time-lapse images, taken by the Cassini spacecraft, show that the northern cyclone has wind speeds of 325 miles per hour, more than twice as fast as Earth’s strongest hurricanes. Says Cassini scientist Kevin Baines: “In a lot of ways, these are the most powerful cyclones ever seen…. They would expand over the whole planet if it was the Earth” [Discovery News].
The source of heat that powers these massive storms is not yet clear; Earth’s cyclones draw heat from the oceans that they drift across, but Saturn’s fixed cyclones have no bodies of water at their bases. They may be driven by Saturn’s internal heat, which can create giant weather patterns by causing massive parcels of atmospheric gases, most likely ammonium hydrosulfide, to rise and fall. It’s also possible that sunlight trapped in the planet’s atmosphere could drive the motions [Science News].
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The Cassini spacecraft that has been busily exploring Saturn and its moons swooped to within 30 miles of the tiny moon Enceladus yesterday, and has already begun sending back images of the fissures near the moon’s south pole. The icy moon, which is about 310 miles wide, has tantalized scientists with geyser-like eruptions of icy water vapor that were first spotted in 2005…. The eruptions produce a halo of frozen water vapor and gas that replenishes Saturn’s E-ring as Enceladus circles the planet [SPACE.com].
The Cassini took images of the fissures, which scientists call the moon’s “tiger stripes,” in the infrared spectrum as well, to gain further information about the temperatures in the vents; previous studies had shown temperatures there can reach a relatively balmy -135 degrees Fahrenheit, which is 200 degrees Fahrenheit warmer than the rest of the moon. While the material sprayed out of the fissures consists of frozen water vapor, scientists disagree on whether an internal ocean of [liquid] water, life’s crucial ingredient, hides within the tiny moon [USA Today].
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NASA’s Cassini spacecraft has discovered a liquid lake the size of Earth’s Lake Ontario on the south pole of Titan, Saturn’s largest moon. Researchers say that Cassini’s instruments reveal that the chilly reservoir … Titan, is composed of a key component of crude oil — liquid ethane [Science News].
The new find supports the common belief that Titan is a promising place to look for extraterrestrial life. 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 [Wired News].
The Cassini orbiter has racked up a number of accomplishments since it began investigating Saturn and its moons in 2004, but its most exciting missions have focused on Titan, where the thick nitrogen and methane atmosphere resembles the atmosphere that existed on primordial Earth.
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