steorra: Jupiter's moon Europa (europa)
[personal profile] steorra posting in [community profile] astronomy
A couple weeks ago, there was news about a new analysis of what's going on under Europa's surface.

We've been pretty sure for a while that somewhere under Europa's surface, there's an ocean. But a big question has been how far under the surface that ocean is. Some facts seemed to suggest that it was quite close to the surface - patches of 'chaos terrain' that looked like ice had broken up, jostled around, and refrozen back together. But other facts implied that the icy shell outside the ocean must be quite thick. It hasn't been at all clear how these apparently conflicting pieces of evidence should be resolved. The new work proposes a model where the icy shell is quite thick, but within the icy shell there are melt pockets - like underground lakes - that cause chaos terrain above them.

As usual, Emily Lakdawalla has a good write-up of it.

More links:
Sky and Telescope: Europa's Subsurface Lakes
University of Texas at Austin: Scientists Find Evidence for “Great Lake” on Europa and Potential New Habitat for Life
The original article in Nature, for those who have subscription access.
A NASA press briefing

On November 6th, 2011, Cassini did a flyby of Enceladus that was devoted to taking synthetic aperture radar (SAR) imaging. This is pretty unusual; normally, Cassini only uses the SAR imaging on Titan, in order to peer through Titan's haze. Since other moons don't have significant atmospheres, SAR isn't important to be able to see their surfaces.

The Cassini website has just released a news item about the flyby; it has a link to a video that shows the radar swathe overlaid upon an ordinary image of the surface, and then shows close-ups of two particular regions of the swathe.

Again, Emily Lakdawalla has a good post about the topic. She points out that the purpose of this is actually more to help us understand Titan than to help us understand Enceladus; SAR is often hard to interpret, and by using it on a surface where we can check what we're finding against visible-light (and ultraviolet/infrared) imaging, we can get a better idea of what SAR images of Titan mean.

EDIT Dec. 2, 2011: Apparently, Cassini has in fact taken SAR images of Enceladus before, as well as of Rhea and Iapetus; however, it seems that the previous images were much lower resolution. Discussion here on the Unmanned Spaceflight forum, with links to images.



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