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Cassini Probe Will Dive Through Enceladus's Water Jets (nasa.gov) 65

An anonymous reader writes: NASA's Cassini probe has a daring mission tomorrow: dive through the water jets spraying from the south pole of Saturn's moon Enceladus. The probe will be a mere 30 miles above the surface, traveling at a relative speed of 19,000 mph. Researchers hope to gain insight into the chemical composition of the jets. "[T]he plumes are more than just gas and water: samples show that they also contain many of the building blocks essential to Earth-like life. This lends itself to the exciting possibility that organisms similar to those that thrive in our own deep oceans near volcanic vents exuding carbon dioxide and hydrogen sulfide might exist on Eceladus." The molecules suspended among the water may tell us whether Enceladus's oceans are capable of harboring life. "The spacecraft's sensors will pick up gases in the plume searching for the presence of molecular hydrogen (H2). The amount of H2 found could reveal how much hydrothermal activity is occurring in the ocean."

Saturn's Moon Enceladus Has Global Subsurface Ocean 72

An anonymous reader writes: NASA's Cassini probe has made another fascinating discovery: Enceladus, one of Saturn's moons, has an underground ocean spanning its entire globe. Researchers were trying to explain why the moon wobbles as it orbits Saturn, and they eventually came to the conclusion that its outer shell must be completely detached from its core. "The mechanisms that might have prevented Enceladus' ocean from freezing remain a mystery. Thomas and his colleagues suggest a few ideas for future study that might help resolve the question, including the surprising possibility that tidal forces due to Saturn's gravity could be generating much more heat within Enceladus than previously thought."

Enceladus's 101 Geysers Blast From Hidden Ocean 39

astroengine writes: New observations from NASA's Saturn-orbiting Cassini spacecraft have revealed at least 101 individual geysers erupting from Enceladus' crust and, through careful analysis, planetary scientists have uncovered their origin. From the cracked ice in this region, fissures blast out water vapor mixed with organic compounds as huge geysers. Associated with these geysers are surface "hotspots" but until now there has been some ambiguity as to whether the hotspots are creating the geysers or whether the geysers are creating the hotspots. "Once we had these results in hand, we knew right away heat was not causing the geysers, but vice versa," said Carolyn Porco, leader of the Cassini imaging team from the Space Science Institute in Boulder, Colo., and lead author of one of the research papers. "It also told us the geysers are not a near-surface phenomenon, but have much deeper roots." And those roots point to a large subsurface source of liquid water — adding Enceladus as one of the few tantalizing destinations for future astrobiology missions.

Waves Spotted On Titan 73

minty3 writes "Planetary scientists believe they have observed waves rippling on one of Titan's seas. The findings, presented on March 17 at the Lunar and Planetary Science Conference, describes how the Cassini spacecraft captured images of sunlight glinting off the Punga Mare (abstract), suggesting they are not reflective sunlight but waves." The Planetary Society recently posted a nice breakdown of the basics about Titan's lakes: "To flow with liquid, those river valleys must have been filled with methane that came from higher elevations; it had to rain methane on Titan. Rainfall runs off, and then what? It must pool somewhere. What we learned from the Cassini orbiter at Saturn is that there are lakes on Titan. ... Rainfall, river runoff, lakes, evaporation into clouds, rainfall again. Cassini has seen clouds make storms on Titan. We have seen the whole cycle -- it's just like Earth's water cycle, but with a completely different substance [methane], and much, much colder."

Saturn In All Its Glory 75

The Bad Astronomer writes "On Oct. 10, 2013, the Cassini spacecraft took a series of wide-angle pictures of Saturn from well above the plane of the rings. Croatian software developer and amateur astronomical image processor Gordan Ugarkovic assembled them into a stunning mosaic (mirrored on Flickr), showing the planet from a high angle not usually seen. There's a lot to see in this image, including the rings (and the gaps therein), moons, and the planet itself, including the remnants of a monstrous northern hemisphere storm that kicked off in 2010. It's truly wondrous."

Craters Quickly Hidden On Titan 39

MightyMartian writes "NASA scientists say Cassini has discovered that far fewer craters are visible on Titan than on the other moons of Saturn. The craters they have discovered are far shallower than other moons' craters and appear to be filling with hydrocarbon sand. On top of being another reason Titan's active geology is very cool, it adds to the mystery of where all the methane on Titan is coming from. 'The rain that falls from Titan's skies is not water, but contains liquid methane and ethane, compounds that are gases at Earth's temperatures. ... The source of Titan's methane remains a mystery because methane in the atmosphere is broken down over relatively short time scales by sunlight. Fragments of methane molecules then recombine into more complex hydrocarbons in the upper atmosphere, forming a thick, orange smog that hides the surface from view. Some of the larger particles eventually rain out onto the surface, where they appear to get bound together to form the sand.'"

The Swirling Vortex of Titan 45

sighted writes "New images from the robotic spacecraft Cassini show the ongoing formation of a massive vortex in the atmosphere of Saturn's planet-sized moon Titan. (See also this animation.) The same moon has recently provided tantalizing hints of an underground ocean as well. Future missions, if any are ever funded, will have plenty to explore."

Is There a Subsurface Water Ocean On Titan? 57

Stirling Newberry writes "Luciano Iess and team have hypothesized that Titan joins Earth, Europa, and Ganymede as ocean worlds. They measured the size of the tidal bulges and found that the moon is likely not solid (abstract). Team member Jonathan Lunine points out that Titan's methane atmosphere is not stable, so it needs some source, perhaps from outgassing. On Earth, water means life, and in the future, ice covered ocean worlds are targets for human colonization. As the late Arthur C. Clarke observed, water is the most precious substance in the universe to humans."

Using Shadows To Measure the Geysers of Enceladus 27

The Bad Astronomer writes "A lot of folks are posting about the amazing new pictures of the icy moon Enceladus returned from the Cassini spacecraft. However, one of them shows the shadow of the moon across the geyser plumes. This has been seen before, but I suddenly realized how that can help determine the geysers' locations, and I thought Slashdot readers might be interested in the general method."

New Close-Ups of Saturn's Geyser Moon 89

sighted writes "Over the weekend, the robotic spacecraft Cassini buzzed Saturn's moon Enceladus and its intriguing geysers. Cassini flew just 62 miles above the moon's surface — and right through its jets of water vapor and ice — both capturing pictures and 'tasting' the geyser plumes. Cassini makes another pass by Enceladus later this month. Even more pictures can be seen in the stream of raw images sent by the probe."

The Rain On Saturn Falls Mainly From Space 75

The Bad Astronomer writes "Astronomers have discovered that the source of water in Saturn's upper atmosphere is none other than the geysers erupting from its moon Enceladus. The geysers spew water into space, most of which is lost. A small amount, though, falls to Saturn... equivalent to only about 7.5 kilos/second over the entire planet (PDF). A typical rainfall on Earth is 42 trillion times heavier."

Saturn's Super Storm 73

An anonymous reader sends in a brief writeup about a massive storm that's been visible on Saturn's surface for a few months now. "As it rapidly expanded, the storm's core developed into a giant, powerful thunderstorm, producing a 3,000-mile-wide (5,000-kilometer-wide) dark vortex possibly similar to Jupiter's Great Red Spot." The storm has been photographed by the Cassini probe, Hubble and even amateur astronomers here on Earth. (The Planetary Society Weblog also posted an 8,000-pixel-wide panorama a while back.) "The violence of the storm — the strongest disturbances ever detected in Saturn's stratosphere — took researchers by surprise. What started as an ordinary disturbance deep in Saturn's atmosphere punched through the planet's serene cloud cover to roil the high layer known as the stratosphere." A study on the thermal structure of the storm (abstract) was just published in the journal Science.

Titan May Have Water Ocean Under the Surface 64

RedEaredSlider writes "NASA's Cassini probe, in orbit around Saturn, may have discovered evidence for a liquid water ocean under the surface of Titan, Saturn's largest moon. The data comes from radar observations of the surface that measure Titan's rotation and tell how it is oriented relative to the plane of its orbit — its axial tilt. According to a paper to be published in an upcoming issue of Astronomy and Astrophysics (preprint PDF at arXiv.org), the new data showed that many of the planet's surface features were in the wrong place, sometimes off by as much as 30 kilometers (19 miles). Titan always presents the same face toward Saturn, just like the Moon does to Earth. But in those situations, one expects that the moon will be in the 'Cassini state,' which means that the axial tilt will have a certain value. In Titan's case, the axial tilt was measured at 0.3 degrees. That seemed too high if one assumed Titan was a solid body."

Titan May Have an Ocean 109

olsmeister writes "Titan has been a particular focus of attention because of its dense, complex atmosphere, its weather and its lakes and oceans. Now it looks as if Titan is even stranger still. The evidence comes from careful observations of Titan's orbit and rotation. This indicates that Titan has an orbit similar to our Moon's; it always presents the same face toward Saturn and its axis of rotation tilts by about 0.3 degrees. This data allows astronomers to work out Titan's moment of inertia and points to something interesting. The numbers indicate that Titan's moment of inertia can only be explained if it is a solid body that is denser near the surface than it is at its center."

Thin Oxygen-CO2 Atmosphere Discovered On Rhea 37

Randyll writes "During its Saturn flyby in March, the Cassini space probe detected an oxygen-rich atmosphere on Rhea, Saturn's second-largest moon. While 100 times thinner than the atmospheres of Europa or Ganymede, Rhea's atmosphere contains a surprising amount of carbon dioxide. There is an explanation for the oxygen — the decomposition of surface ice — while the origin of the carbon dioxide is a mystery. A few of the possible explanations are that Rhea has carbon-rich organic molecules or that the gas is seeping from Rhea's interior. However, researchers have been unable to determine the exact source for the gas." While "richness" is relative — the study's abstract refers to Rhea's atmosphere as "tenuous," and oxygen concentrations are trillions of times lower there than they are on Earth — the finding still puts Rhea in rare company among the planets and moons of the solar system.

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