Emily LakdawallaOct 04, 2011

Brief notes from Day 2 of the DPS-EPSC meeting

It's been a very full day at the 2011 joint meeting of the Division of Planetary Sciences / European Planetary Science Congress (DPS/EPSC). My day was less full than it might have been, because I overslept and missed most of the morning's session. I really needed the rest though so I think it was probably for the best!

I came in toward the end of a session featuring results from both Hartley 2 and Tempel 1 flybys by Deep Impact and Stardust, respectively. Mike A'Hearn told me later that they'd intentionally mixed up the Hartley 2 and Tempel 1 talks to emphasize that they were studying comets, not missions. Today's press briefing also included some from these two comets.

A few highlights: Mike Belton showed that all of the 380 "quasi-circular features" (also known as "pit") that have been mapped on Tempel 1 could have been produced as one outburst per perihelion passage. Outbursts appear to occur preferentially on elevated terrain.

Deep Impact high-resolution view of Hartley 2
Deep Impact high-resolution view of Hartley 2 Deep Impact took this photo of Hartley 2 near the closest approach of its flyby on November 4, 2010 at 13:59 UTC.Image: NASA / JPL / UMD

At the press briefing, Mike A'Hearn and Lori Feaga stated that they have now confirmed that the two lobes of the dog-bone-shaped Hartley 2 have distinctly different chemical composition, with a strong signal of jets of carbon dioxide emanating from the smaller lobe throughout the comet's 17-day rotation, and not coming from the larger lobe; the larger lobe did not "turn on" cometary activity when it rotated into sunlight.

After lunch I started in the Kuiper Belt Object (KBO) sessions. The KBOs were relegated to one of the conferences smaller rooms, and it has been overflowing throughout the meeting. It opened with Bruno Sicardy presenting some very interesting results on a stellar occultation by Eris, but I can't write anything more about that because he asked people not to share details until they were published in Nature on October 26. Throughout the rest of the afternoon the other scientists kept referring to how Sicardy's information changed some of their comparisons between Eris and other KBOs, so the rumor mill is probably already pretty leaky. But I won't break anything until somebody else breaks it.

Ortiz presented on a really nice multichord occultation by Makemake, and a new estimate of its size: an ellipse with poorly constrained equatorial diameter 1610 +22/-180 kilometers and a much better constrained polar diameter of 1444 ± 9 kilometers. Quaoar, too, got a new size estimate from Braga-Ribas. He found it to be bigger than previously thought, 1045 to 1084 kilometers. But the fit of an ellipse to the many chords that they got in their occultation was poor; it looked like Quaoar had a big bite taken out of it. This was puzzling to everyone, but someone in the audience asked if it could be a contact binary, and he said they could not rule it out.

Then I moved on to the Titan session. Stephan Le Mouelic presented the work that's been done to make a global map of Titan with VIMS data, and promised that there would be more, very high resolution VIMS data on upcoming orbits.

Ralph Lorenz looked at the puzzle of the similarity of Titan's lake terrain to Florida's karst -- it's a puzzle because Titan's "rocks" are made of water ice which is not soluble in liquid ethane. But, Ralph said, it's possible that a minor constituent of the lakes might act like a "soap," helping polar water molecules dissolve in a nonpolar ethane solvent.

Back in the Pluto session, the most interesting talk was by Tom Mueller, who talked about Makemake as the most exotic KBO. He showed that in order to fit the very good Herschel and Spitzer data, Makemake needs to have a surface that is a patchwork of some material that is as reflective as the surface of Eris (higher than 95% albedo) and other material that is as dark as a comet's surface. This is an even greater contrast than we see on Iapetus.

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