Posted on 07/19/2005 11:15:30 AM PDT by LibWhacker
The Cassini spacecraft has coasted to its closest encounter yet - skimming just 175 kilometres above Saturn's icy moon Enceladus. But astronomers are at a loss to explain its observations.
On 14 July, Cassini swooped in for an unprecedented close-up view of the wrinkled moon. Its Imaging Science Subsystem (ISS) camera has since returned pictures of a boulder-strewn landscape that is currently beyond explanation. The "boulders" appear to range between 10 and 20 metres in diameter in the highest-resolution images, which can resolve features just 4 m across.
“That’s a surface texture I have never seen anywhere else in the solar system,” says David Rothery, a planetary geologist at the Open University in Milton Keynes, UK.
Cracks crisscross Enceladus's surface - possibly as a result of the moon being repeatedly squeezed and stretched by the gravity of Saturn and other moons nearby. But Rothery points out the boulders avoid - rather than fill - the cracks. This might indicate that the fracturing took place after the boulders had already formed.
Alien landscape
John Spencer, a Cassini team member at the Southwest Research Institute in Boulder, Colorado, US, agrees that the images are puzzling. “You would expect to see small craters or a smooth, snow-covered landscape at this resolution," he told New Scientist. "This is just strange. In fact, I have a really hard time understanding what I’m seeing.”
NASA scientists have been locked in discussions since 15 July and are expected to pass judgment on what they think this peculiar surface might be later on Tuesday.
But Elizabeth Turtle, a Cassini imaging team member at the University of Arizona in Tucson, US, warns there will be no quick answers. “Trying to figure out what is going on is going to take a lot longer than a weekend of swapped emails,” she says.
Heat source
These images - like those from previous flybys - reveal a surface clawed with fractures and swollen with ridges. It could point to a substantial heat source within the moon, driving the internal convection of ice. And this raises the possibility that Enceladus could possess a sub-surface ocean similar to that on Jupiter's moon Europa.
That could be a problem, according to Spencer. Superficially, the two worlds bear a passing resemblance, but Enceladus is six times smaller than Europa. “Enceladus seems too small to have enough internal heat to create a sub-surface ocean," he says. "But, since we don’t understand the surface, we might not understand the interior either,” he says. Turtle, however, is sceptical of the ocean hypothesis and says "we see no evidence of liquid flows on the surface”.
Key information in this debate may come from Cassini’s Dual Technique Magnetometer. It was fluctuations in Europa’s magnetic field that finally convinced scientists that it harboured a subsurface ocean. Perhaps the same will be true of Enceladus. At present, the data is being analysed by scientists at Imperial College in London, UK.
Regardless of the outcome, NASA has already decided that Enceladus is worth an even closer look. They have scheduled another grazing flyby of the moon in 2008, when Cassini will skim even closer than ever - to within 100 km of the boulder-strewn surface.
Our Moon is actually quite dark. It only seems bright in comparison to the surrounding sky. Venus is far brighter, as are several other objects including Europa and Enceladus.
Ever wonder what a foreign probe would find swooping the grand canyon? - I wonder if they would call is "bizarre boulders" or majestic view?
albedo... n : the ratio of reflected to incident light
So the albedo of a celestial body isn't a measure of the total brightness of the body, but a measure of its reflectivity as a percentage of incident radiation. Thanks for bringing this up!... I learned something today, too. :-)
The first forms of colony life on earth were formations like toadstools. Could the boulders be concretions made by lifeforms--bacteria?
No, that would be the moon Clintobius.
Caramba! Some big enchiladas there!
Has the latter ever really been established?
Or are the "scientists" piling theories on top of hypotheses on top of guesses (again)?
Ooh, Moravian sugar cake! Just look at that crumb topping. The butter holes are the best part, though.
I just saw something about that on the Science Channel last week. They spoke of it as if it were an established fact (based, I think, on a quick and dirty radar study of the moon). They did make the point, however, that the depth of the "ocean" wasn't known, nor is it known whether or not the ocean is slushy ice all the way down to the seabed or liquid at some point below the surface. I think all the 'ifs,' 'ands,' and 'buts' clearly puts it in the realm of educated speculation at this point.
Now you've made me hungry! :-)
Well . . . let's send up a manned mission I guess and drill cores. 8^)
LOL! Good One
I'm not hungry anymore, thanks.
That crossed my mind! Seems conceivable at the very least, and it'd certainly be a most unexpected discovery. Alas, some unidentified geologic process seems far, far more plausible.
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