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Fraser
2005-Feb-17, 06:08 PM
SUMMARY: Just two days after visiting Titan, Cassini swept past another Saturnian moon: Enceladus. The spacecraft got within just 1,180 kilometers (730 miles) of the bright moon. Enceladus is unusual because of the high reflectivity of its surface, which resembles freshly fallen snow. But in this close-up view, the best ever taken, it has a much more wrinkled look. Enceladus is only 505 kilometers (314 miles) across.

View full article (http://www.universetoday.com/am/publish/close_up_enceladus.html)

What do you think about this story? Post your comments below.

antoniseb
2005-Feb-17, 06:45 PM
Wow! Great pictures. I was looking at them over on the Cassini site, and came back here to post some, but as anyone familiar with UT would guess, they were already up!

It's interesting that the surface looks so much like the forzen top of a muddy puddle, except that the scale is thousands of times larger. The low number of visible craters suggests that Enceladus must have at least partially melted relatively recently.

Duane
2005-Feb-17, 07:42 PM
It looks surprising like Europa or Ganymede! The lack of craters suggests this is a pretty young surface.

VanderL
2005-Feb-17, 08:32 PM
Lack of what (http://ciclops.lpl.arizona.edu/media/ir/2005/853_1860_1.jpg) precisely? :D

There is a very stark difference in cratering between different regions on Enceladus, the difference is clearly visible in the above link.

Cheers.

JB
2005-Feb-17, 08:44 PM
Is it me or do the meteorite craters appear to be the wrong way around? i.e. they appear to be "bumps" rather than "dips". If so this would seem to fit in with antoniseb's observation that the surface is like a "frozen muddy puddle".

You can almost imagine a meteorite hitting, making a splash and the surface re-freezing as it rebounded back up.

antoniseb
2005-Feb-17, 09:20 PM
Originally posted by JB@Feb 17 2005, 08:44 PM
Is it me or do the meteorite craters appear to be the wrong way around?
Looking at the image VanderL provided, the light is coming the wrong way for the eye to judge the craters as dishes as opposed to bumps. If you capture the image and use some image-tool to turn it upside down, it will look like craters again.

Note that VanderL has gotten an image which shows a region WITH craters adjacent to a region without craters, and so while Duane is right about the particular part of the surface being young, clearly it is not ALL so young. Nice image VanderL.

VanderL
2005-Feb-17, 09:20 PM
Matter of the angle of light, sometimes it helps to look at the image upside down (eh.., the image upside down, not you).

Cheers.

Kurt Tate
2005-Feb-18, 03:38 PM
Check out the shadow on the channel wall above the "craters", then the location of the shadow at the craters. If the light source is at the top of the photo then the craters are actually hills.

Kurt

antoniseb
2005-Feb-18, 04:12 PM
Here's a New Scientist story about this that suggests that tidal disruption has caused regions of the surface to be sometimes flooded with amonia-water.

Images show Enceladus is a 'geologist's paradise' (http://www.newscientist.com/article.ns?id=dn7029)

alan
2005-Feb-19, 04:29 AM
Ive read that the surface is nearly pure water ice with very little ammonia. The ammonia was susposed to act like antifreeze. Without it they will need to find a much larger energy source to explain how the ice was melted to the surface.

VanderL
2005-Feb-19, 10:56 AM
So now we need not only ice volcanoes to explain the high albedo, but also ammonia acting as anti-freeze and don't forget they also need Saturn's and Dione's gravity to act on Enceladus in a specific way as to provide the heatsource. And there is also the puzzle how some regions can be completely cratered (and remain so for a very long time) while others show signs of being melted and refrozen repeatedly. I say there is no end to the evidence that our solar system is chaotic and violent in a way that constantly surprises the theorists.

Cheers.

antoniseb
2005-Feb-19, 03:30 PM
Originally posted by VanderL@Feb 19 2005, 10:56 AM
I say there is no end to the evidence that our solar system is chaotic and violent in a way that constantly surprises the theorists.
I agree. There are plenty of things out there to study. Plenty of very interesting new details to observe.