Ceres High Altitude Mapping Orbit (HAMO), Late summer through fall 2015 Options

[Holder of the Tw...]

DAWN arrived in its new lower mapping orbit on August 13th. The DAWN team is preparing to resume science observation tomorrow on the 17th.

From the Current Mission Status page at the DAWN website:

August 13, 2015 - Dawn Arrives in Third Mapping Orbit

Dawn completed the maneuvering to reach its third mapping orbit and stopped ion-thrusting this afternoon. This was a little ahead of schedule because the spiral descent went so well that some of the allocated thrusting time was not needed. Since July 14, the spacecraft has reduced its orbital altitude from 2,700 miles (4,400 kilometers) to approximately 915 miles (1,470 kilometers). The orbit period has correspondingly decreased from 3.1 days to 19 hours.

Dawn is scheduled to begin its new observations on the evening of Aug. 17 (PDT) and continue for more than two months. First, however, the mission control team will measure the actual orbit parameters accurately and transmit them to the spacecraft.

[dvandorn]

Yes -- Both Spudis and Wilhelms (two of my favorite lunar science authors) give kudos to Baldwin. And wasn't it Baldwin who, after holding stubbornly to other theories for a time, finally pronounced Barringer Crater an impact feature?

I completely agree, Baldwin is seminal for impact theory. And much of the later work, from many people including the above-mentioned, has expanded on the dynamics of ejecta formation and re-emplacement, shock effects on the impact targets, and development and emplacement of impact melt sheets on rocky bodies and also on hydrated rocky bodies like Earth and Mars. And on the propagation of energy into the impact target, something I think is key to the festures we're seeing on Ceres. I think a lot of the cryovolcanism we're seeing might be the result of impact-generated temporary heating and agitation of Ceres' icy mantle (or perhaps subsurface ocean/convecting warm ice mantle), causing sudden movement and eruption of subsurface materials.

It appears that there has also been ejecta splash resurfacing going on around the larger basin-forming impacts. And the large, extremely relaxed basins we see wouldn't just have relaxed like that immediately -- the impacts would have moved and displaced a lot of the material around and below the impact site, which would have pushed back in (and up) to raise the basin floors back up. That movement would affect the entire mantle in one way or another, and I bet it would cause cryovolcanic processes and features.

Of course, all of this assumes that Ceres has some kind of either liquid or convecting warm ice mantle, and makes some assumptions about how globally contiguous of a unit it is. I'd be interested to see if some of the first papers to come out on Ceres from the Dawn data will deal with the qualities of the mantle deduced from the imagery and the spectroscopy...

-the other Doug