Posted on 01/10/2005 7:05:00 AM PST by holymoly
A giant ridge girdles Saturn's satellite Iapetus - making the moon look like a walnut shell - reveal the latest images from the Cassini-Huygens mission. Scientists are at a loss to explain the feature, which is unique in the solar system.
The Cassini spacecraft flew past Iapetus on New Year's Day, approaching to within 123,400 kilometres of the moon's surface. Its camera captured the most detailed images of Iapetus yet, revealing wisps of dark material and two-tone craters. But the ridge is the greatest surprise to scientists.
It extends for at least 1300 km, following the equator exactly. In places the ridge breaks into mountains at least 13 km high - far taller than Mount Everest on Earth and among the highest known on any world.
But no one knows how the ridge formed. It might have been pushed up by compressive forces like fold mountains on Earth, or erupted from a crack in the crust like Earth's mid-ocean ridges.
This new mystery may have some connection with an old one, the two-faced nature of Iapetus.
The moon is unusual in that one half of Iapetus is bright white, presumably where the surface is clean ice, and the other half is pitch black. This dark side is the leading face of the moon - that is the half of the moon which leads in Iapetus's orbit around Saturn. Dark materials
It is not clear where this dark, carbon-rich material came from. It might be soot blasted off an outer moon and then swept up by Iapetus, or it might have erupted from inside Iapetus itself.
Cassini's latest images offer details, but no clear solution. They show that the dark hemisphere has wispy edges. Images also reveal that craters on the dark side tend to have two-tone walls, with those facing the equator covered in dark material, while those facing the poles remain light. Both of these observations could fit either theory for the origin of the dark material.
The spectrum of the dark material is also inconclusive, showing features reminiscent of material from two different types of asteroid.
There is one new clue, however. The images show that the material lies in a very thin layer, which rules out one kind of eruption theory in which liquid from the interior may have filled up a vast basin on one side of the moon. So if the dark material did come from Iapetus, it must have erupted in plumes of dust or droplets that spray-painted the surface. It is quite possible that those plumes were spewed out in whatever cataclysm created the bizarre ridge
Cassini will return to Iapetus in 2007 for a much closer view, skimming just 1000 km above the surface. But its next job is to act as a relay station for the Huygens probe, which is on course to plunge into the atmosphere of the giant moon Titan on Friday. Huygens aims to analyse Titan's enigmatic surface, and sniff out complex organic chemistry that might shed light on the origin of life on Earth.
Hey, it's just after the holidays. We're all bulging a little bit at our "equator". Give Saturn's moon a bit of a break until around March at least. : )
It's made of metal and that is where the two halves are welded together.
8^)
That's no moon... It's a space station.
;o)
Looks like the Death Star.
Darn, you beat me to it. :P
Iapetus's got a woody!!!
Good L-rd. I think I'll start that rumor among the Conspirazoid set.
That always happens after the Holidays...
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Old news. Tin foil folk even believe our moon is a hollow spaceship . . . |
"Kahk A Moon"!
I have a bad feeling about this...
;^)
Maybe there's a toy inside.
A giant ridge girdles Saturn's satellite Iapetus - making the moon look like a walnut shell
the answer is in the first line - girdle; must be time for a new one
that I am a total idiot!
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