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Iapetus Rocks
Iapetus, home of the Stargate in the
Arthur C. Clarke 2001 books, finally got it's close-up
The Cassini orbiter took a good close look at Iapetus on September 10th, and the moon continues to be one of my favorites. What's not to like about it? It has weird colors, strange ridges, an odd shape. It's the strangest moon in the solar system. Here are some more pics from the Cassini album.
Looks like something out of my refrigerator from my college days,
but it's not. This image shows terrain in the transition region between
the moon’s dark leading hemisphere and its bright trailing hemisphere.
"The side of Iapetus that faces forward in its orbit around Saturn is being darkened by some mysterious process," said John Spencer, Cassini scientist with the composite infrared spectrometer team from the Southwest Research Institute, Boulder, Colo.
Once the leading side is even slightly dark, thermal segregation can proceed rapidly. A dark surface will absorb more sunlight and warm up, explains Spencer, so the water ice on the surface evaporates. The water vapor then condenses on the nearest cold spot, which could be Iapetus's poles, and possibly bright, icy areas at lower latitudes on the side of the moon facing in the opposite direction of its orbit. So the dark stuff loses its surface ice and gets darker, and the bright stuff accumulates ice and gets brighter, in a runaway process.
Scientists say the result is that there are virtually no shades of gray on Iapetus. There is only white and very dark.
Snow on a side of a moon made of coal?
The images are very interesting
What is that dark stuff? And why is Iapetus so starkly contrasted between light and dark?
That mysterious ridge line has craters, which means it's not something new
This image of the equatorial mountains was taken at a distance of about 2,400 miles. Each square pixel in the image covers and area about 75 feet by 75 feet.
The equatorial ridge is quite a mystery. Was it partially destroyed after it formed, or did it never extend all the way around the moon? Scientists have ruled out that it is a youthful feature because it is pitted with craters, indicating it is old. And the ridge looks too solid and competent to be the result of an equatorial ring around the moon collapsing onto its surface. The ring theory cannot explain features that look like tectonic structures in the new high resolution images.
More of the light/dark contrast
This picture looks almost normal
"Our flight over the surface of Iapetus was like a non-stop free fall, down the rabbit hole, directly into Wonderland! Very few places in our solar system are more bizarre than the patchwork of pitch dark and snowy bright we have seen on this moon," said Carolyn Porco, Cassini imaging team leader at the Space Science Institute, USA.
I have to agree.
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