[X] My Assistant

[Guest_AlexBlackwell_*]

The T25 flyby page is now online; however, so far as I can tell, the mission description document isn't available publicly yet.

[dvandorn]

What we need to know to be able to properly interpret this latest lake image is whether or not the SAR mode can actually penetrate the surface of the liquid we're looking at. If it does penetrate, how deeply does it penetrate?

I'm frankly having a hard time believing that the lower portion of this lake is actually filled with liquid. Look at the upper portion, which is obviously liquid-filled -- there is a spit of linked islands near the center of the image, very near the top. You can see absolutely nothing of the formation which, logically, must connect this spit of islands beneath the lake surface. They completely disappear at what appears to be the surface level of the liquid. It's certainly the horizon at which the radar ceases to "see" through the liquid. There is no darkening, no "bathtub ring" around the bases of these spit islands, to indicate that we're looking through the surface of the liquid (as you would expect if the lower portion of the image is seeing submerged terrain). The break in visibility between the "seeing horizon" and the spit islands is sharp and well-defined.

Also, in the lower portion of the image, there are several locations which reflect just as darkly as the liquid surface above, and they tend to be arrayed in arroyo-like formations. These *could* just be drainage formations that are, indeed, currently submerged, but again, it's really hard to say when you don't know how deeply the radar may be penetrating the liquid's surface.

Without any convincing data about how far the radar can penetrate this liquid, I'm pretty certain that the lower portion of the image is not currently flooded, but that the radar-dark material that seems to complete the lake shore is actually sedimentation from recent flooding. (Also, some ripple-like formations in this darkened terrain look as much like dunes as they look like liquid-flow ripples. Brings to question how much of the time this terrain really spends submerged.)

In addition to the question of whether the entire region is submerged, I'm fascinated by the flecks in the liquid surface in the upper portion of the image. They seem to be more concentrated closer to the shorelines. Are these blocks of ice floating on the liquid? Would the local ices even float in this liquid? Or could these flecks actually represent wave action on the surface of the liquid?

Think of it -- waves on the lakes of Titan...

-the other Doug