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2008-Jul-09, 06:32 PM
University of Maryland: Study Puts Solar Spin on Asteroids, their Moons & Earth Impacts (http://www.newsdesk.umd.edu/scitech/release.cfm?ArticleID=1691)


Asteroids with moons, which scientists call binary asteroids, are common in the solar system. A longstanding question has been how the majority of such moons are formed. In this week's issue of the journal Nature, a trio of astronomers from Maryland and France say the surprising answer is sunlight, which can increase or decrease the spin rate of an asteroid [YORP effect].

[The authors Derek Richardson and Patrick Michel] outline a model showing that when solar energy "spins up" a "rubble pile" asteroid to a sufficiently fast rate, material is slung off from around the asteroid's equator. This process also exposes fresh material at the poles of the asteroid.

If the spun off bits of asteroid rubble shed sufficient excess motion through collisions with each other, then the material coalesces into a satellite that continues to orbit its parent.