Tuesday, July 26, 2005

New Enceladus Image: Tiger Stripes Up Close

CICLOPS has released this high resolution frame showing the "tiger stripes" near Enceladus' south pole. These stripes were first seen as albedo features in images taken in May (though their northern ends could be seen in images taken in March). This image has a resolution of 122 meters/pixel and was taken from a distance of 20,720 km from Enceladus. It shows the tiger stripes to be fractures cutting across the Enceladean south polar region with ridges on each side of the fractures in many cases. The tiger stripes are distinctive in color observations as blue-green stripes. Blue-green terrain, thought to be coarse-grained water ice, has been observed in other region within bed-ice outcrops and canyon walls. Here, the blue ice appears to be a mattling, not just in fractures, but in relatively flat terrain as well. The cause for the difference in distribution is still under investigation.


Anonymous Pioneer said...

Do you all think these "tiger strips" formed the same way the cracks on Europa did?

7/26/2005 07:23:00 AM  
Blogger Jason said...

The tiger stripes do bear a resemblence to so-called double ridges on Europa, both at low resolution and at high resolution. Now whether that means that they formed the same way is a good question. At low resolution, both have dark material surrounding a bright stripe (leading to these features on Europa being called "triple bands" after the Voyager flybys). But the color of the dark material is very different, dark red on Europa, probably due to non-ice contaminents, and blue on Enceladus due to the prevalence of coarse grained water ice. Both have a "double ridge" surrounding a fracture appearance, but the Enceladean tiger stripes seem less...neat, the ridge margins are much more convoluted, at least compared to Europan ridges I'm familiar with.

So there are a number of similarities but also some key differences so it may be difficult to say whether they formed in similar ways. But I am VERY hesitant to say that this means Enceladus has an ocean. Remember, as I said earlier this month, the large regions of cratered terrain suggests that there are at least some regions where a sub-surface ocean does not appear to be present. Sure, you can always point to Callisto, a world with a dead surface geology but has a sub-surface ocean, but it is quite deep. Deep enough that it would be problematic for Enceladus given its small size.

7/26/2005 10:08:00 AM  

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