Tuesday, April 05, 2005

New Titan Image: New Titan Territory

CICLOPS has released sharpened view (shock a sharpened view of Titan I didn't make) from last Thursday's flyby. This view shows the H-region on Titan, a feature first discovered by ground-based observers a few years before Cassini's arrival. Cassini, prior to this encounter, had observed the southern portion of this mosaic at moderate resolutions, but the H itself has not been viewed at higher resolutions that 60 km/pixel. This image, at 7 km/pixel, is but a taste of what's to come as this is one of the Wide-angle images taken during a medium resolution mapping that show these same features at even higher resolution (5x higher than this image). However, Cassini RADAR has SAR swaths that do cover this area. The Ta SAR swath covers the very northern portions of this image and while the T3 swath covered low to mid northern latitudes.

Some features in common can be seen in this image and in the T3 SAR swath. The dark spot with a patch of bright terrain just right of center is the 80-km wide crater seen by RADAR. though it appears that some of the details on the shape of the "ejecta blanket" may differ between the two instruments.

So I'll open this image up for discussion, though you may want to wait a day or two...


Anonymous Phil Stooke said...

One comment right away - detail is visible all the way to the terminator. The earlier near-full phase views had the terminator near the limb where the depth of atmosphere hides things. It's not impossible that high resolution optical images of the same area near both morning and evening terminators could be 'differenced' to show some effects of topographic shading. It would be very subtle, though, with all that scattering. But not impossible.

4/05/2005 02:29:00 PM  
Blogger Jason said...

without giving to much away, yes we can see features out to about an incidence angle of 80 I think. You start bringing out more noise once you go past about 70 and the noise dominates past 80. In terms of differencing, you still have the problem where the atmosphere effectively scatters light across the entire sky. For example, the DISR sun sensor kept losing lock on the sun at lower altitudes because there was very little difference in the brightness of the sky between looking near the sun and away from the sun. But near sun rise and sunset, there maybe enough of a difference to bring that out in a ratio

hmm, we'll look into that. The only problem is that our flybys often have very similar geometries such that I am not sure when we get a flyby where the sunrise terminator is near 0W, where the sunset terminator is in these images (and in T0 if you click on the first link within my post above.

4/05/2005 02:44:00 PM  
Anonymous Gsnorgathon said...

It looks like there's a general trend of NW-SE-oriented features, as there is on the anti-Saturnian hemisphere. Do you suppose there will be SW-NE-oriented features in the southern hemisphere?

It also looks as though the small crater does have a parabolic feature extending to the SE. The bright area immediately around the crater is more or less circular, but there's a more diffuse, parabolic penumbra.

Aeolian features? Or am I reading too much into the data?

4/05/2005 04:13:00 PM  
Blogger Jason said...

There are some NW-SE trending dark features within the intermediate brightness terrain between 15N and 30N in both this image and in the T3 MONITOR mosaic. I will be more willing to talk about these features later in the week. Stay tuned.

Now the bright diffuse deposit SE of the 80-km crater, in this case I think you could make the case for it being a parabolic penumbra, but I think we still need to take into account prevailing wind direction (using the long axis of the dunes in RADAR and the assumed direction of west-east) the parabola doesn't seem to match either. But certainly that is one possibility that has crossed my mind.

4/05/2005 04:53:00 PM  
Anonymous Gsnorgathon said...

You know, I'd forgotten about those dunes. They do make things a bit more interesting, don't they? One of the really big cans of worms that brings up is the whole notion of climate change on Titan. We know Venus, Earth, and Mars haven't had the same climatic conditions for their entire history, and we know Earth and Mars have had quite a bit of climatic variation recently. So maybe Titan too. We certainly could have two different sets of aeolian features (if that's what they are) based on different climate regimes. Fun stuff to puzzle over.

4/05/2005 10:21:00 PM  
Blogger Jason said...

The idea that Titan's atmosphere has changed over time has come up. However, I think we have more work to do before we think about whether that is a penumbra (first I would like to know which direction that meteor came from, I think the islands to the east and the shape of its ejecta blanket could give us clues to that).

4/06/2005 11:04:00 AM  

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