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January 18, 2005

Titan update - part of the puzzle comes together 1/17/05

From John Strickland:

Very early on Sunday, Jan 16, someone apparently leaked a bunch of additional Titan photos, and they went out on the web. Immediately, a bunch of amateurs started to fit them together and quickly produced several map-like mosaics. Late on Sunday, ESA released most of the remaining photos on its web site. It is still not clear if the count of 350 photos refers to just the descent photos, or all those taken after landing. These are shown in sets of three. It looks as though one of the downward-pointing cameras has taken close-up pictures of the "soil" under the probe, lit by the 20 watt lamp.

The big news of Sunday is that we now know where the channels go. They drain towards the dark-colored flat terrain after all. If one frame in either direction from the original frame of the dendritic terrain had been shown, we would have seen at least one channel emptying into what now seems more and more like a "dead sea bottom". With the new mosaic maps, the coast-line looks more and more like a real coastline, with capes and bays, many with channels emptying into them. In a few of the photos, very narrow channels can be seen, indicating that there are range of channel sizes. We can see almost 10 places where channels empty into the dark area. Most of the rocks near the probe are rounded, which makes it look like the action of a liquid environment. However, there is no liquid to be seen in any of the photos so far. The mosaic maps do make it quite clear that we landed on the dark, flat terrain. However, we have not yet found the images taken just before landing, which would prove that the light bands are indeed made of loose surface rocks.

This leaves us to wonder where did the ethane go (or whatever once filled the shallow sea)? Indications that the nitrogen in the atmosphere is enhanced in heavy isotopes could mean that most of the regular nitrogen has been lost. If this is true, then the atmospheric pressure might have been much greater in the past, perhaps allowing even ammonia-water seas. However, if the flow of liquids stopped long ago, then we should see considerable cratering across Titan. An unlikely possibility is that the seas have just dried up, and that the cratering process has just begun. Another is that the surface wind blows around enough loose material to fill in any craters. Finally, Titan may go through warm and cold phases, with enough liquid present in a warm phase to allow surface dynamics to continue to erase craters.

Once all the images have been assembled and enhanced, some of these questions may be answered. Eventually, the Cassini probe will be able to get a radar scan across the landing site, and we will be able to match the radar image with the optical ones. Other questions will have to wait for the next Titan mission, perhaps 10 or 20 years in the future. One possibility for a future mission would be a Titan balloon, which would float below the haze layer, giving an excellent close-up optical view of the a large sample of the surface. Another would be a Titan orbiting imaging radar mission, similar to the one sent to Venus. Since Titan is a whole world, larger than Mercury, but cloaked in clouds, it will take a long time to extract all of its secrets. Involvement of the International Science Community, like the ESA, which was largely responsible for this stunning success, will help speed up that process.

Posted by apsmith at January 18, 2005 11:09 PM



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