By Jeanna Bryner
Senior Writer
posted: 24 June 2009
01:03 pm ET
Posted on 06/24/2009 11:30:05 AM PDT by tricky_k_1972
|
Ocean Hidden Inside Saturn's Moon By Jeanna Bryner Senior Writer posted: 24 June 2009 01:03 pm ET
|
Astronomers have found the strongest evidence yet for an ocean beneath the icy shell of Saturn's Enceladus, suggesting it could join the exclusive club of watery moons in our solar system.
The salty water is likely feeding jets of water-ice that spurt from the moon's south polar region. Such plumes were first reported in 2005, and ever since, astronomers have suspected a liquid ocean might lie beneath the icy shell of Saturn's sixth largest moon.
The new finding, published in the June 25 issue of the journal Nature, could bump this diminutive world — measuring 310 miles (500 km) in diameter (about the width of Arizona) — into a class that includes Jupiter's Europa, Ganymede and Callisto.
In addition, the water and other key life ingredients such as organic material found in the plumes, could provide a suitable environment for life precursors, said lead researcher Frank Postberg of the Max-Planck Institute for Nuclear Physics in Heidelberg, Germany.
Supersonic jets
Four years ago, an analysis of data from NASA's Cassini spacecraft at Saturn revealed the water-ice jets that spurt from four fractures called tiger stripes, each extending some 75 miles (120 km) across Enceladus's south polar region. The jets shoot thousands of miles into space, with some of the ice grains and water vapor escaping the moon's gravity and ending up in Saturn's outermost ring, the E ring.
In fact, some of the authors on the new paper reported last year in Nature that the water vapor jets blast out much faster than the dust particles, with the vapor reaching speeds rivaling a supersonic jet — about 650 to 1,100 mph (300 to 500 meters per second). That finding suggested Enceladus had an ocean below its surface.
Now, evidence points precisely to such a salty body of water. The results come from data collected by the Cosmic Dust Analyzer instrument aboard Cassini, which showed sodium salts within ice grains of Saturn's E ring.
The composition of different sodium compounds and overall salt levels correspond with what the scientists would expect if there were an ocean beneath the moon's icy shell.
"If you have liquid water in contact with a rocky core, then salts would be the most abundant dissolved compounds," Postberg told SPACE.com. "The only way to get that much salt into water is to extract it from rock."
Not the Atlantic
While Postberg and his colleagues are not sure about the size of this ocean, even if it covered the southern hemisphere, the water body would be small compared with Earth's oceans. It would also be a little less salty than, say, the Atlantic or Pacific oceans, Postberg said.
And as far as swimming, a thick wetsuit would be in order, as the water would be close to freezing, he said. (That's warmer than the moon's surface, which reflects 100 percent of the sunlight striking it and plunges to minus 330 degrees Fahrenheit — minus 201 degrees Celsius.)
In another study published in the June 25 issue of Nature, researchers report results from ground-based observations of the vapor cloud in Saturn's E ring, rather than the ice grains. These observations didn't show any sodium in the vapor. The finding, however, doesn't exclude the possibility of an Enceladan ocean.
Instead, the team argues that if the plume vapor does come from ocean water, the evaporation must happen slowly deep underground, rather than as a violent geyser erupting into space. That's because a violent saltwater geyser would eject sodium into the vapor cloud, and the results show no such sodium.
"The original picture of the plumes as violently erupting Yellowstone-like geysers is changing. They seem more like steady jets of vapor and ice fed by a large water reservoir," Postberg said. "However, we can't decide yet if the water is currently 'trapped' within huge pockets in Enceladus' thick ice crust or still connected to a large ocean in contact with the rocky core."
Postberg and his colleagues say such steady jets are either fed directly by an ocean-like body of water or from reservoirs connected with that ocean.
Cassini flybys planned for the fall could glean more information on the ocean-geyser link, he said.
/mark : )
He chose moons, rather than the planets they orbit, as the site of future colonies.
It's hard to judge from just one solar system, but it looks like oceanic moons might incredibly common throughout the universe.
I would imagine the sheer number of moons is also going to be much greater than the number of planets, again using our solar system as the sole example. We have about 170 moons to eight planets.
I think the idea has been around for a while. In the book HER NAME, TITANIC by Dr. Charles Pellegrino (1988), Pellegrino is having a conversation on page 62 with Titanic wreck discoverer Robert Ballard, and says: “We’re almost certain that Saturn’s moon Enceladus has an ocean of liquid water under the ice, and probably Jupiter’s Europa.” (How was this relevant to the Titanic? Pellegrino was suggesting that Ballard’s use of robotic deep-sea submersibles showed the way for how the ice-moons of the outer planets could be explored.) Anyway, I’m not enough well-informed about the state of planetary science 21 years ago to know what led to Pelligrino to say that Enceladus probably had an internal ocean then, but such speculation must have been forgotten during the interim since the recent discoveries by the Cassini probe that Enceladus might have liquid water seem to have taken everyone by surprise.
space ping
"The original picture of the plumes as violently erupting Yellowstone-like geysers is changing. They seem more like steady jets of vapor and ice fed by a large water reservoir,"
So they're essentially suggesting a continuous evaporation process, due to the lack of sodium in the vapor cloud. The lack of gravity from such a small object would demand that the continuously growing cloud of vapor could not remain captured by the moonlet, else it would have a thick atmosphere.
Perhaps this moon was the size of Jupiter (or larger) in it's past, given that our solar sytem is "Billions" of years old, right?
Either that, or the rate of vaporization has changed (i.e. dramatically sped-up recently)
Or perhaps this moon is a new arrival, trekking across the galaxy with a big load of water until it was captured in our solar system.
Or, heretically, our solar system is considerably newer than speculated upon by many.
I would bet that something has changed, but what. I know that they have been theorizing that this is being caused by a pocket of radioactive material; it's possible that this was shifted closer to the surface do to seismic activity.
Ummm, Cheese Enceladus
Groan. Oh you will pay for that, of yes, you will.
How many times does this have to be rediscovered? Is their financing in doubt again?
A water ice comet, captured long ago might end up that way.
"In a second study, also in Nature, a team led by Nicholas Schneider of Colorado University likewise looked for salts in Enceladus' plumes, this time using spectrographs on Earth-bound telescopes.
That it failed to detect any would seem to challenge Postberg's findings, but the Earth-based observations -- combined with the Cassini data -- may in fact give us additional clues as to how they may be true, said Spencer.
It tells us, for example, that the plumes could not have been formed by boiling salty water spewing directly out of Enceladus' tiger stripes, otherwise the sodium would be so abundant as to be observable from Earth.
Instead, the plumes could come from salty water distilling into fresh water vapours, but not through evaporation as happens over Earth's oceans, but rather in pressurised chambers under the moon's surface."
Who wrote this article?
The albedo of the moon is 0.39.
It reflects 39% of the sunlight, not 100%.
Formed?
Tons of ice pellets hit the Earth every second, every day, and probably have since time began.
If they pelt the Earth, they pelt every astronomical body in space.
I think they are talking about Enceladus’s surface, not our moon, and since Enceladus’s surface is mostly ice it very well could reflect almost all the sunlight that gets to it.
Formed as in how the water (not the ice) that is being dispelled in the geysers formed, as in did it form in the cracks in the surface or is there a larger deposit of liquid water under the surface that eventually makes it to the surface where it is expelled.
Thank you. My mistake. You are absolutely correct.
Which do you think it is?
I truly don’t know, I hope it’s below the surface and that it is a persistent feature, that would make it alot easier for life to form and be more interesting to study.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.
