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As of today there is, to my best knowledge, not a single confirmed rubble pile -- the weblink to the JAXA-page, in particular, is quite misleading (Itokawa can be seen to be as boulder-strewn as Eros is, but a rubble pile is another thing!). Sure, there is bits and pieces of evidence, such as the low mass density of Mathilda or other asteroids, the nearly-spherical shape of many binary asteroids, and the cut-off of determined rotation rates at the Roche-limit. But still the existence of rubble piles is not entirely sure so far. If nobody minds I'll rewrite the article along these lines -- once I'm done with the German version, that is. --DerHerrMigo 20:54, 17 December 2005 (UTC)
Sounds like you know what you're talking about. But speaking as a non-expert ... Itokawa certainly looks like ... a pile of rubble. The Singing Badger 21:39, 17 December 2005 (UTC)
Why are some asteroids rubble piles and some not?
It seems to me that you could fairly well predict if an asteroid is going to be a "rubble pile"/a low density void structure, by knowing its orbital history around the sun, i.e its rate of outgassing. As I can imagine that with say, a quick baking/the creation of a strong voided structure is part of the reason why "rubble piles" are not consolidated yet. By contrast, if the asteroid is slowly baked/the void structure does not turn out to be so supportive or rigid, then gravitational processes would make consolidation easier. I got thinking about this after doing some editing on Foam concrete as I seem to remember reading about it being used as a target substitute in light gas gun impact testing and a bit about this hypothesis. Although maybe I'm mistaken as my search engine didn't produce any hits. Boundarylayer (talk) 11:41, 20 August 2015 (UTC)