Dawn's first orbit, including RC3, March 6, 2015- June 15, 2015 Options

[Ron Hobbs]

Dawn is now officially in orbit around (1) Ceres!

Congratulations, NASA. Nice images of crescent Ceres.

NASA Spacecraft Becomes First to Orbit a Dwarf Planet

[Phil Stooke]

It's right next door to its basin (left edge)! And there is another much more subdued but even larger basin at top center in your cropped image. Besides, on a small object like Ceres basin ejecta can cover a hemisphere, it doesn't need to be that close.

Also, don't be taken in by the 'fresh' appearance of the ejecta. Look at the ejecta of Orientale on the Moon. Old but remarkably fresh-looking.

Phil

[Gladstoner]

It's right next door to its basin (left edge)! And there is another much more subdued but even larger basin at top center in your cropped image. Besides, on a small object like Ceres basin ejecta can cover a hemisphere, it doesn't need to be that close.

Also, don't be taken in by the 'fresh' appearance of the ejecta. Look at the ejecta of Orientale on the Moon. Old but remarkably fresh-looking.

I've been straining to interpret the stuff as ejecta and other impact effects, but some things seem 'off'.

- The 'tilled ground' seems to have an irregular or even patchy distribution. The edges appear abrupt in some cases. Ejecta usually grades into the surrounding terrain in a regular manner -- or so it seems/appears, at least.

- There are no obvious source basins for the ejecta/tilled ground. Nearby candidate craters/basins are either partially covered in the stuff, or appear too old or degraded. I was eagerly awaiting to see a dramatic basin on the image released on May 4, but instead was disappointed by a barely visible outline.

- The crater size distribution is odd. I would expect more small- and medium-sized craters on ejecta from a degraded basin.

- Speaking of crater size distribution, I'm still amazed by the number of large craters around the south pole. What 'happened' to all the smaller ones (that seem to 'prefer' the north pole)?

- The curved valleys are a surprise. I would expect straight valleys (grabens or crater chains) on a primitive body like Ceres. Slumping causes curved grabens, but that doesn't seem to be in play here. My eyes even see 'spiral' patterns of valleys surrounding a couple basins, but more imagery is needed to address that....

- I look forward to more puzzling questions in the coming days, weeks and months....