Did Fluid Once Flow on Titan?
January 14, 2005
|Surface image from Titan shows ice blocks strewn around. Click image for larger view. Image Credit: ESA|
Carolyn Porco of the Space Science Institute (Boulder, Colorado) heads Cassini’s imaging science team. She sat down with Astrobiology Magazine’s Chief Editor, Helen Matsos, to give a scientist’s first look at Titan from the European Space Agency’s Darmstadt, Germany mission control room.
Porco, also an University of Arizona adjunct professor of planetary sciences, describes her excitement and surprise when the Mars-like imagery first beamed down to Earth from Titan’s surface. Porco speculates what might elementally comprise those mysteriously smooth boulders in the foreground.
Helen Matsos (HM): What is your reaction to the stunning photos from Titan today?
Carolyn Porco (CP): I sound like a broken record, but I am so shocked! I really didn’t expect Titan to look this way. I really didn’t expect the images to be so easily interpretable.
HM: What did you think they’d look like?
CP: I thought we’d see patterns like we’re seeing only in finer details and I thought they’d still be mysterious to us. But the images that we’ve seen, one of them is clearly a drainage pattern. I mean, what else could it be, it doesn’t take a rocket scientist, right? Secondly the other one looks like Mars! I totally didn’t expect it, it looks like Mars!
So I’m thinking it can’t be silicon rocks — it’s not Mars really — it can’t be silicon rocks.
Because if Titan is a differentiated body, and it’s got to be differentiated because it’s big, it would be ice on the outside and all the rocky material would have fallen to the inside. So it can’t be silicon rocks– it has to be ice.
|Carolyn Porco, Imaging Team Lead. Titan is unlike Mars and the icy moons of Jupiter, which have little or no atmosphere. So the "techniques that we’ve used for interpreting airless bodies, all those methods of examining solid surfaces from planetary spacecraft that we have learned over the last half century," don’t apply, says Porco. "We can’t use that on Titan, because it’s a very different environment."
Image Credit: NASA/JPL
So it’s ice rocks: But the ice rocks, you see them, they look flattened, they look for all the world like normal rocks except they can’t be silicate rocks. So what could they be? They are ice rocks, maybe they got tumbled in a river of some sort, who knows? Maybe there was a flood plain like we see on Mars…, but it’s just unexpected, very unexpected. I’m still having a hard time absorbing it. I can’t wait to see what they have tomorrow.
HM: In terms of the quality we are getting back, what kind of resolution can we expect for future images that have been more heavily processed? Will they change in terms of refinement?
CP: These first pictures we’ve seen, they are not going to improve any more. They have put out their best in terms of a sample. But I would imagine that to put together the kind of mosaic they want to put together it takes a lot of work. That’s why we’re not seeing that tonight. Those poor people, I’m just glad it’s not me! I’m just enjoying this and they are having to do all the work! They will probably stay up all night long and be beat by press time tomorrow.
But boy are they going to have a story to tell! It is going to be one hell of a day. It sounds trite, but this is way more than I expected. I was hoping for some glimmer of a chance that their data were going to help us interpret ours. But I think now some of the things that we are seeing make a lot more sense to me.
HM: Such as?
CP: Such as these features that we see in the South Polar region which look long and meandering… And my first impression, and I’m not a geologist, was it looked like a meandering stream. But as a scientist you don’t say that unless you have ample evidence — because it just looks like a curvy line, right? But this thing that we’ve seen today looks so much like a drainage pattern, now that we’ve got the fine details. It can’t be tectonic so almost by default it has to be something that flowed to cause those channels.
|The very bright features near Titan’s south pole are clouds similar to those observed during the distant Cassini flyby on July 2, 2004. Image Credit: NASA/JPL|
HM: So what fluid do you think it was that created those patterns?
CP: I suppose lava tubes could do this. If there were vulcanism you could get lava tubes — because you see meandering things like this on the moon, and they are not depressions, they’re more raised tubes. In fact you see this even in Hawaii, where you can see collapsed lava tubes –there was a big vacant tube and then it just collapsed. That’s because the stuff on the outside cools faster than the stuff on the inside, so the stuff on the inside keeps flowing until there is no more, but the stuff on the outside forms a crust — that’s called a lava tube. I suppose these meandering patterns could be those too now that I think about it, but again, what would be the lava….? You’d expect the outside of Titan to be icy.
HM: Are you saying it is seemingly not icy?
CP: No, no, I can’t say– seemingly not, the pattern could be carved in ice. This is not new. People have theorized that there would be stuff falling out of the atmosphere and there would be liquid ethane-methane combos falling out of the atmosphere carving channels and gullies… I did a little captain’s log on my web site about this, which is just a synopsis of what people have been saying for years — so it looks like maybe that’s what we’re seeing? I just didn’t think it was going to be so clear. I said the same thing during Saturn orbit insertion about the ring images — I mean, I’m batting zero!
I thought we were going to see a lot of squishy kind of patterns and still not really know what they were. Again, I guess it could be a lava tube.
It is a drainage pattern of some sort, but given what people suspect about the atmosphere it’s probably a fluid…. But the question is: is it a fluid flowing right now? Or something from long ago? Who knows?