Icy moon and distant rings

Icy moon and distant rings

Icy moon and distant rings

Bad Astronomy
The entire universe in blog form
March 17 2011 7:02 AM

Icy moon and distant rings

[REMINDER: I'm guest hosting Dr. Kiki's Science Hour today at 4:00 Pacific time!]


Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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Ya know, for a tiny ball of ice, Saturn's moon Enceladus really knows how to pose for a picture:

Cassini snapped this shot from 34,000 km (20,000 miles) away, looking down on the northern hemisphere of Enceladus. Peeking just over the edge is a slice of Saturn's rings, too.

Most of the action on Enceladus is at the south pole, where geysers of water are erupting. But up at the other end of the 500 km wide moon -- for comparison, Colorado is 600 km across -- it's still pretty nifty. The reflective, icy surface is saturated with craters, including that interesting triple smackdown on the left. Something must have broken apart as it hit... though I'll note the two big craters are elongated, indicating a very shallow angle of impact, while the third smaller one is round. It may only coincidentally line up with the other two. If that's the case, maybe a binary asteroid hit here long, long ago.

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Cracks snake their way across the surface too. Enceladus certainly has liquid water under its perpetually frozen exterior, though there's some debate over whether it's a global ocean or pockets of liquid. Still, the remarkable thing is that a moon smaller than some states and frozen to a temperature of -200°C could still have liquid water hidden beneath at all. I remember, as a kid, reading books by scientists wondering if we'd find water in space. Cripes. It's everywhere!

Image credit: NASA/JPL/Space Science Institute



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