This is CBS I Am The World. I'm John Batcher and this is Hotel Mars episode N, Dr. David Livingston

of the space show, Dr. Space and I are co-pilot. And we have a navigator with us, Dr. David

Grinspoon, who has been my guide on the matters of the solar system, especially the possibility

of astrobiology for many decades. And there's always new information coming in, which makes

planetary science endlessly interesting. You have all this data that you know in 100

years, they're still going to be processing it, but it's fresh when you see it. And what's

fresh right now is that Juneau, which is the NASA probe of Jupiter, been in orbit, has

now given us pictures of Ganymede, a very large moon. The distinguishing characteristic

of these photographs is that it has cracks in the surface that look like somebody's been

skating over it. Dr. Grinspoon, what do we make of these cracks? We've seen this before.

Well we've seen it before, but this is a wonderful new close-up look. I mean, our first

decent views of Danemy, they weren't quite this decent, but the first time we really

saw what the picture was like, goes back to the Voyager mission in 1979, when Voyager

did its flyby through the Jupiter system. But then in the 90s, we had the Galileo probe,

which was a Jupiter orbiter, which made many passes by Danemy and got us a lot of great

images. But we haven't been back there with a decent camera since then. So it's been

decades, and it's one of the seat Ganymede again with this incredibly sharp camera of

the Juneau mission. You mentioned that what they call the groove terrain, those cracks

in the surface, that sort of parallel cracks that characterize a big fraction of the surface.

And that groove terrain is actually a big mystery. It's still really unexplained, even though

we've had the images of it since the Voyager days. There are ideas that they are some kind

of tectonic ridges left over from early in the history of Danemy when the icy crust was

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