Surface Changes on Titan

Okay, true, Titan is off-topic here but still I can't pass up an opportunity to mention a paper that was published today in Geophysical Research Letters (in which I am second author of) reporting the discovery of active playa in the south polar region of Saturn's moon Titan. We also released a press release on this. While counting and measuring dark features in the south polar region last year in preparation for a Titan paper, I found that some of these features were in one observation from June 2005 but not in the other from July 2004. If these were small features, I could discount them as being due to resolution effects and the effects of the atmosphere that blurs out details, but these changes were much too large. You can see what I am talking about on the Planetary Photojournal.

It didn't take us long to figure out what we were looking at, a real surface change on the surface. We surmise that this change resulted from a rainstorm that dumped enough rain over this spot on Titan to flood the valley floors with a shallow layer of liquid methane. The most likely storm (that we are aware of, keep in mind that we don't have continuous coverage) to have caused this was a massive storm system seen from Earth and by Cassini ISS in early October 2004. The brightest part of the storm (and plausibly the most intense part of the storm with the greatest cloud heights) was located over this surface change in the ISS observation of the storm on October 8, 2004.

Anyways, even though it was off-topic, I thought I would quickly share this here.

Link: Cassini Finds Hydrocarbon Rains May Fill Titan Lakes [ciclops.org]

DPS Meeting so far

Despite still being in Tucson, for the last few days I have been remotely attending the DPS meeting in Ithaca, New York. The DPS meeting (otherwise known as the Meeting of the Division of Planetary Science of the American Astronomical Society... *phew*) is one of the big three American planetary science meetings, which also includes LPSC (generally in March), the AGU Spring Meeting (generally in May), and the AGU Fall Meeting (generally in December). I attended the DPS meeting last year, and even gave a talk on the Cassini camera's observations of Titan's trailing hemisphere.

So this year, I am watching the DPS meeting online via Cornell University's Live Webcasting system. No Io-related results in the talks presented so far, but there were quite a few sessions I was interested in. First and foremost for me were the Titan sessions. In fact, it seems like Titan has replaced Mars in importance at DPS with three Titan oral sessions versus just one Mars surface session.

Perhaps the talks that had most relevence to Io in these Titan sessions were the "Subsurface" talks given yesterday morning. Many of these talks related to surface processes generated by internal activity, such as topography, mountains, and cryovolcanism. The cryovolcanism talks, given by Rosaly Lopes, Bob Nelson, and Ashley Davies, often sounded like Io talks from a few years ago. Lopes discussed RADAR results at a feature known as Hotei Arcus, seen above in ISS data from July's T45 flyby. The RADAR team inteprets some of the features in the region as cryolava flows, composed of water and ammonia. The flows appear to be part of a compound flow field, similar to Amirani and Prometheus on Io. The main body of the flow field appears bright in RADAR, indicating a rough surface. On top of this flow field are several large flow lobes that are darker, or smoother, than the rest of the flow field.

Bob Nelson gave a talk on the photometry of Hotei Arcus and a region in western Xanadu. These two regions correspond to areas where RADAR has seen evidence for compound flow fields. Based on a comparison of several observations acquired by VIMS, Nelson suggests that brightness changes have been observed at these regions, possibly due to fumerolic activity at these sites. With the addition of the RADAR results, Nelson's finding are becoming a lot more convincing. Finally, Ashley Davies presenting a cooling model for cryolava flows on the surface of Titan, similar to cooling models he presented for Io in recent years.

The Galilean Satellites session takes place Wednesday morning starting at 8:30 am EDT (5:30 am Tucson time). You can catch it live or archived following the talk by following this link. The only Io surface-related talk to be given tomorrow is by Julie Rathbun. She will talk about ground-based observations of Loki at multiple wavelengths. I will present a summary on the blog tomorrow afternoon. Also, tonight, the NASA Night session will be presented online at 7:30 pm EDT (4:30 pm Tucson time). These are always pretty interesting. I am not sure if the Outer Planets flagship mission will be discussed, but you can presume the recent headaches over the Mars Science Laboratory will.

Link: DPS Meeting main link [dps08.astro.cornell.edu]