I've been following on Twitter some of the things being reported at the joint conference of the American Astronomical Society's Division for Planetary Sciences
and the European Planetary Science Congress (DPS-EPSC). I'm sure things will come out in a more refined form at some point, but here are some of the things reported that have caught my attention.
First of all, before my own extractions of stuff from Twitter, some stuff by people who know more than I do.
Emily Lakdawalla has written up a post
on first impressions, including stuff from talks on Enceladus and Vesta. Some highlights mentioned in her post are: large salty grains in Enceladus's plumes make it pretty much certain that the plumes have a liquid source; Vesta doesn't have any moons larger than 10 metres diameter; and results for the mass, volume, density, and probable core size of Vesta. Also, Vesta's surprisingly colourful, as solar system objects go.Three official press releases:
A press release
about results from Dawn's mission to Vesta. An additional interesting piece of information from it is that surface temperatures have been measured from 240K to 270K. That's roughly -30° Celsius to 0° Celsius. (I'm assuming these are only dayside measurements, and that temperatures would become much colder during the night, but the press release doesn't actually say that.) There are lots of images and diagrams linked at the bottom of the press release.
on 'snow' (actually really really tiny ice particles) on Enceladus.
And a press release
on the Kuiper Belt Object 2001 QG298. It's a contact binary - two objects touching each other. This was figured out in 2004 because of changes in its brightness when it rotated; it was rotating nearly edge-on to us, so that one of the two objects sometimes hid the other from view. At first they didn't know if it was rotating in the same plane as its orbit, in which case it would stay nearly edge on, or at an angle to its orbit, in which case the fact that we were seeing it edge on is because we're lucky enough to catch it at the right part of its object. Since it was discovered, the changes in brightness have diminished significantly, indicating that it's rotating nearly at right angles to its orbit, and thus we were just lucky to catch it. This hints that there may actually be a lot of contact binaries out there.
And now for some interesting tidbits from Twitter, sometimes with some context added; it's quite possible that I've gotten some things wrong in processing tweets into what I say below, so it should be taken with a good dose of grains of salt. Among other things, it's often hard to be sure from a tweet whether something is a tentative suggestion or something solidly evidenced.About Vesta:
There are three kinds of meteorites on earth thought to come from Vesta: howardites
, and diogenites
(grouped together as HED meteorites
). Dawn's results so far indicate that the global spectrum of Vesta is more like that of howardites than of diogenites or eucrites. Regionally, the south of Vesta is more like diogenites than the north is. (The Wikipedia article on diogenites indicates that diogenites are thought to be from deep within Vesta. In that case, it makes sense that they would be found in the south, where the giant impact would remove a lot of the overlying surface.) Also, there are east/west differences in how eucrite-like Vesta is.
Spectral variations on Vesta are often associated with geological features, and spectra indicate the presence of pyroxene
Vesta is estimated to have regolith
1.5-5 km deep; this estimate comes from crater shapes.
Dark material on Vesta occurs in craters, but also elsewhere. Where it comes from is still uncertain. Some possibilities: carbonaceous
impactors, or volcanism, or both.
Initial indications are that Vesta has less water than Earth's Moon; this will be better determined once Vesta gets into Low Altitude Mapping Orbit.About Titan:
The carbon isotope ratio on Titan is similar to that on Earth, according to Cassini data.
Titan's upper atmosphere has lots of heavy, negative ions. No one's sure yet how they get there.
The Huygens probe
measured an electrical field in Titan's atmosphere that shows that Titan's crust is 60-80 km thick.About Kuiper Belt Objects:
On 36% of KBOs, water ice has not been detected.Varuna
's thermal (infrared) lightcurve is correlated with its visible light lightcurve. I'm not entirely sure of the significance of this but I'm guessing that one thing it indicates is that the major variations in Varuna's lightcurve are due to its shape, and not to differences in how bright different parts of it are.
Twitter accounts I used in compiling the above (I hope I haven't forgotten any):Emily LakdawallaasrivkinDavid MintonFranck MarchisEuroplanet MediaMeg Schwamb