Thursday, February 8, 2007

Weather Forecast for Titan: Cloudy. For 25 Years...

Try to visualize a single cloud covering the sky stretching from Lisbon to Rome...
Hard to get the picture ain’t it?
The Cassini spacecraft imaged one with that size (2400kms in diameter) on Titan’s North Pole.
Associating clouds this size with the lakes discovered in the previous year, we are closer to understand the process conducting to the filling and drying of those lakes.

Dr. Christophe Sotin, from the University of Nantes and member of the visual and infrared mapping spectrometer team (VIMS) help us drawing a portrait of what is going on Saturn’s most exciting moon.

Know more about Cassini-Huygens.


A doubt, the cloud has become visible as spring arrives but it was already there hidden from view, correct?

-Yes, this is correct. It was observed from Earth-based telescopes. But of course, it did not have the resolution we have with VIMS and we do see many more details and structure.

Could you describe what would we see on the surface of Titan below this gigantic cloud?

-With VIMS, we cannot see below the cloud. But radar saw lakes on areas below the cloud.

Is it raining over there?

-We haven't seen the rain. But theoretical work predicts rain. But it is a model.

And how would it rain? Snow-like features?

-We haven't seen the rain. But when we look at the South pole where a similar cloud was present 5 years ago, we do not see something like snow.
But we are still processing the data and this is not a definite answer.
More data are still to come.

And on the velocity this cloud is moving, any data already?
How does it interact with the almost stillness of the atmosphere nearer the surface?

-Not yet.
We are working on models describing the dynamics of Titan's atmosphere and the relationships between the clouds at 40° latitude and the polar clouds.

25 years, that is a long period...In what is based the conclusion pointing to that cycle's duration?

-We have observations since the Voyager mission, 25 years ago. And we see the variations between the South and the North Pole.

In that 4 to 5 years period in between the lakes will get drier and drier, is that it? What is the process involved?

-Apparently, on one lake, we see a shoreline at higher elevation and it looks like the lake is drying out.
However, we will try to get another radar image at the end of the extended mission (2010) in order to compare the level of material in the lakes.

Any answer so far for the differences in lake's population from the North to the South Pole?

-Not yet. Actually, we may not have paid enough attention to the South pole and we are going back to the data in this area.

What can we expect to know more from the following 16 fly-bys?
Is there a focused search on a specific question?

-Well, the nominal tour was already designed and the sharing between instruments is not going to be changed. What we may do, is to change the pointing according to what has been discovered. Also, the findings have been important in order to choose between the options we had.

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