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Mission: Hayabusa 2
post Yesterday, 10:32 AM
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QUOTE (Paolo @ Jun 17 2018, 09:49 AM) *
I wonder if the apparent equatorial ridge is merely an effect of Ryugu spinning around the axis of maximum inertia, or if it formed from loose material pooling on the equatorial plane as in the case of asteroid Steins.
we will soon know: if the ridge is cratered the former is true, if it's smooth it's the latter. I am betting on the latter, as equatorial ridges seem to be common on small, relatively fast-spinning objects.

Is that the case at Steins? It seems fairly uniformly cratered (including the equator) as far as can be seen at the limited resolution available

I think certainly the case for ring-embedded moons (e.g. Pan, Atlas and Daphnis) but for obvious reasons in their case. I'm going for the former for Ryugu.

Just a guess though smile.gif

Edit: Have just been reading about the 'YORP' effect, as regards the shaping of asteroids over time - I'm surprised this can be inferred for Steins' shape bearing in mind the resolution of available imagery during the Rosetta flyby though....
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post Yesterday, 11:33 AM
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quoting from the abstract for "E-Type Asteroid (2867) Steins as Imaged by OSIRIS on Board Rosetta" (the full article is beyond the paywall, I have a pdf of it somewhere)

Steins is not solid rock but a rubble pile and has a conical appearance that is probably the result of reshaping due to Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) spin-up. The OSIRIS images constitute direct evidence for the YORP effect on a main-belt asteroid.
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Phil Stooke
post Yesterday, 04:39 PM
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That should be regarded as an opinion, not an established fact. It may be true but the images only suggest it, they don't prove it.


... because the Solar System ain't gonna map itself.
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