Huygens News Thread, News as and when we find it Options

[rlorenz]

"Since the dust was easily lifted, it was most likely dry, suggesting that there had not been any ‘rain’ of liquid ethane or methane for some time prior to the landing."
This seems to be in contradiction with earlier results showing the presence of liquid methane in the soil, close to the surface.

A refinement, not a contradiction (I am a co-author of the DISR work just published, led by Stefan Schroeder and Erich Karkoschka). Titan is (consistently) interesting enough to defy the simplest descriptions.

It rains sometimes, not often. The subsurface was damp, the top few mm were not. Go to a beach a couple of days after rain and you'll see the same sort of thing (except the evaporation timescale may be very different for Titan).

The dust kicked up and indicated in the DISR optical instruments for a couple of seconds seems consistent with the thin fluffy layer indicated by the penetrometer.

[JRehling]

The error bars are still quite large, and will remain so until we've surveyed Titan for a half-Titan-year (we're at about 1/4 so far, with gaps), but there are estimates of total volume of precipitation, and precipitation per storm, plus the constraints we have on the frequency of such storms (we've seen one very large one). When I was reading the literature, looking for a consistent model that fit those various constraints, it seemed to fit if the equatorial regions experience rare, but very large storms, which deposit hurricane-like quantities of rain. A given location in the equatorial regions might go a very long time between storms, on the order of perhaps 80 to 400 years, with each storm soaking about 1% of Titan's equatorial regions. Those numbers are poorly constrained, but should set the expectations that Titan precipitation timescales do not need to be earthlike, and are probably much longer, although the driest deserts on Earth may present similar timescales.

There is reason to suspect that at least one kind of fine particulate condensate is drifting downward, covering exposed surfaces very slowly, providing optical depth on a scale similar to that of the rainfall. A rainfall would wash the fluffy condensate downstream, although what the drying process entails is wide open to speculation.

There's no real constraint on how long the near subsurface could remain wet after a rainfall. The Huygens landing site, which was on some of the relatively rare VIMS-dark-blue terrain might even be near the liquifer table.

[B Bernatchez]

Another new animation of the last moments of Huygens' descent has been released. http://www.jpl.nasa.gov/news/news.php?release=2013-019. Enjoy.