Along with Jupiter’s infamous moon Europa, Saturn’s moon Enceladus is one of the most fascinating places in the Solar System, with its huge geysers of water vapour erupting from cracks in the surface at the south pole. The massive plumes are now thought to originate in a subsurface ocean or sea of salty liquid water, similar perhaps to Europa’s underground ocean. Now, new analysis is providing a more detailed look at the chemical makeup of this unique alien environment and its potential to support life.
(My first article for AmericaSpace, republished here.)
Until relatively recently, it was thought that the best, or perhaps only, place to look for life elsewhere in the solar system was Mars. The other inner planets were much too hot while the outer gas and ice giants were far too cold – the chances of any kind of life being found, even microbes, was considered extremely unlikely at best.
Along with Jupiter’s moon Europa, a tiny Saturnian moon, Enceladus, has become one of the most fascinating places in the solar system and a prime target in the search for extraterrestrial life. Its outward appearance is that of a small, frozen orb, but it revealed some surprises when the Cassini spacecraft gave us our first ever close-up look at this little world – huge geysers of water vapour spewing from its south pole. The implications were thought-provoking: Enceladus, like Europa, may have an ocean of liquid water below the surface. Unlike Europa however, the water is apparently able to make it up to the surface via fissures, erupting out into space as giant plumes.
Now, a new project sponsored by the German Aerospace Center, Enceladus Explorer, was launched on February 22, 2012, in an attempt to answer the question of whether there could be life on (or rather, inside) Enceladus. The project lays the groundwork for a new, ambitious mission being proposed for some time in the future…
See Universe Today for the full article.
Saturn’s tiny moon Enceladus was the centre of attention for the Cassini spacecraft again last week, with beautiful new photos being released of the moon and its water vapour geysers erupting from the south pole. Some views show surface detail on the moon, some are of the geysers themselves and there is a very nice shot of Enceladus silhouetted against Saturn and its rings in the background. There is even a dual ultraviolet stellar occultation in which two of the stars in the belt of the constellation Orion are seen shining through the plumes! Even though these are still raw, unprocessed images, they again capture the beauty of Enceladus and the Saturnian system…
See Universe Today for the full article.
Until fairly recently, the search for life elsewhere in the solar system has focused primarily on Mars, as it is the most Earth-like of all the other planets in the solar system. The possibility of finding any kind of life farther out in the outer solar system was considered very unlikely at best; too cold, too little sunlight, no solid surfaces on the gas giants and no atmospheres to speak of on any of the moons apart from Titan…
See Universe Today for the full article.
(Note: this and future articles written for Universe Today are exclusive, therefore only a summary is posted here, which will link to the full article on UT).
Enceladus, a small icy moon of Saturn, is one of the most active places in the solar system, with dozens of geysers of water vapour and ice particles erupting from warmer fissures near the south pole, a big surprise when they were first discovered by the Cassini spacecraft several years ago. Since then, the debate has focused on their origin, but the latest evidence continues to indicate that the most likely explanation is that the plumes emanate from a subsurface reservoir of liquid water which somehow stays heated enough on this cold world to remain liquid.
A new study indicates that the geysers have probably been active for up to 100 million years. This estimate is based on the fact that a deep layer of snow blankets much of the moon, which forms when ice particles from the plumes settle back onto the surface. The “snow” is a very fine powder which coats the surface at an average rate of less than one thousandth of a millimetre per year. Yet in places the snow is 100 metres thick. This means it must have taken tens of millions of years to accumulate this much, and that such long-lived activity is most easily explained by a reservoir of liquid water beneath the surface.
Other evidence previously discussed also points to liquid water, notably that the plumes are composed of water vapour and ice particles with large amounts of salts mixed in, very similar in composition to salt water oceans on Earth. There are also various organic molecules in the plumes found by Cassini (which has flown through and directly sampled the material in them), and the combination of water, heat and organics have made Enceladus a new favourite spot in the search for extraterrestrial life.
It was also noted during the Division of Planetary Sciences / European Planetary Science Congress (DPS/EPSC) meeting going on now, that the mass of the plumes being primarily slower, salt-rich particles and the amount of ice particles in the plumes also both support a liquid water origin (courtesy of Emily Lakdawalla’s Twitter feed).
Cassini also just took some new photographs of the geysers which are actually like a very fine mist, but look dramatically beautiful when backlit by the sun.
This article was first published on Examiner.com.
The Cassini spacecraft has found the best evidence yet that a salty ocean lies beneath the surface of Saturn’s moon Enceladus. As previously reported, Cassini had analyzed the icy particles being ejected from the water vapour geysers at the south pole in 2008 and 2009, with very interesting results, but now has found that the ones furthest away from the moon contain little salt, but the ones closer to the moon’s surface have much more salt, sodium and potassium specifically, and have a composition very similar to ocean water on Earth. The new study is in this week’s issue of the journal Nature.
To quote the article:
“There currently is no plausible way to produce a steady outflow of salt-rich grains from solid ice across all the tiger stripes other than salt water under Enceladus’s icy surface,” said Frank Postberg, a Cassini team scientist at the University of Heidelberg, Germany, and the lead author on the paper. When water freezes, the salt is squeezed out, leaving pure water ice behind. If the plumes emanated from ice, they should have very little salt in them.”
“The data suggest a layer of water between the moon’s rocky core and its icy mantle, possibly as deep as about 50 miles (80 kilometers) beneath the surface. As this water washes against the rocks, it dissolves salt compounds and rises through fractures in the overlying ice to form reserves nearer the surface. If the outermost layer cracks open, the decrease in pressure from these reserves to space causes a plume to shoot out. Roughly 400 pounds (200 kilograms) of water vapor is lost every second in the plumes, with smaller amounts being lost as ice grains. The team calculates the water reserves must have large evaporating surfaces, or they would freeze easily and stop the plumes.”
The “tiger stripes” are the long fissures that the geysers emanate from. At its closest, Saturn is just over a billion kilometres from Earth. It was previously thought almost impossible that liquid water, never mind an ocean, could exist so far from the sun. But, as theorized, between tidal stress from Saturn and inner radioactive decay, that’s exactly what is on Enceladus (and Jupiter’s moon Europa and possibly others). And what about similar moons that may exist orbiting some of the many other gas giant planets being found in other solar systems? The geysers of Enceladus would appear to literally be ocean spray, a long way from home…
The mysteries of Saturn’s moon Enceladus just get more puzzling… it’s been known for a while now that the water vapour/ice geysers at the south pole emanate from fissures where heat is continuously leaking, more than was thought possible for such a tiny world. Now, new data from the Cassini spacecraft shows that much more heat than that even is coming out of Enceladus’ interior.
The expected heat energy output from tidal heating, based on a 2007 study, was about 1.1 gigawatts (averaged out over time). Plus maybe another 0.3 gigawatts from natural radioactive heating. But the new results indicate an energy output of 15.8 gigawatts, about 2.6 times the energy from all of the hotsprings in Yellowstone, or 20 coal-fueled power stations. For a tiny, icy body like Enceladus, that’s amazing, and also makes it even more likely that the geysers originate from a subsurface sea or ocean. A salty one at that, as salts have already been found in the vapour/ice plumes, as well as organic molecules. What else might be lurking below?
See also the Enceladus image gallery for more great photos.
As noted earlier, I missed posting more the last few weeks due to being sick, but here is a condensed summary of some of the other recent interesting updates as we come to the end of 2010…
Does Pluto, of all places, have a subsurface ocean? This new report says maybe; Cassini has found new evidence for an ice volcano on Titan; the building blocks of life could possibly form on Titan’s surface more easily than thought if there is any liquid water temporarily on the surface from ice volcano eruptions (or comet impacts); there’s a new theory on how Iapetus may have obtained its odd equatorial ridge; the “arsenic life” discovery continues to be criticized by some other scientists (see also here) while the scientists involved have responded and rebutted those claims (see also here); the Spitzer space telescope has found the first known carbon-rich exoplanet; a fourth large exoplanet has been photographed orbiting a star 129 light-years from Earth; another smaller exoplanet, a “super-Earth” was found to have an atmosphere with either high clouds or hot steam; a new study says that the entire Tharsis Rise on Mars should be named the largest known volcano in the solar system instead of the current Olympus Mons (one of four volcanoes that are part of Tharsis Rise); the warm fissures on Enceladus, the source of its water-ice geysers, were seen up-close by Cassini again; there may be another Jupiter-sized planet hiding out in the outer solar system; and finally, the current known exoplanet count is now 516 (and the hope was for at least 500 by the end of this month)!
Highlighted by, among other things, the next exoplanet update from Kepler in February and the launch of Curiosity, the next bigger and better Mars rover, in November, 2011 should also be an interesting year…
A new study suggests that the water-ice geysers on Saturn’s moon Enceladus originate from a bubbly, salty subsurface sea or ocean, a variation of previous theories.
From the article:
“Matson and his colleagues came up with a computer model that accommodates much of what is known about the geysers of Enceladus. Their findings support the supposition that a salty sea flows under the moon’s surface.
This ocean has gases dissolved in it, the theory goes. As the seawater flows up to and through the tiger stripe fissures, its pressure drops and the gases bubble up, Matson said — making the ocean fizzy, like Perrier. The relatively warm water and expanding gas feed the jets.
When the bubbles pop, they throw off a fine spray that contains salt and other materials, which Cassini spotted in Enceladus’ plumes. Then the seawater, having dumped much of its warmth on the moon’s surface ice, cools and sinks back through cracks, rejoining the ocean and its heat-transferring circulation system.”