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| | Science News: Radar reveals an asteroid's strange shape |
 | | Of the 56 asteroids he has studied by radar during the past decade, 23 are Earth-crossers--including three or four whose radar signatures, though not as detailed as those of 1989 PB, at least suggest concavities that could signify large craters or other low spots, he says. |
 | | "Probably sometime within the last 100 million years," says Ostro, noting that the orbits of most "Earth-crosser" asteroids probably evolved no longer ago than that, "there was a big, violent collision between objects in the main asteroid belt [lying between the orbits of Mars and Jupiter]. |
 | | Analysis of the asteroid's shape should "let us make some statements about how tightly gravity is holding the two lobes together and begin to formulate theories about how it was formed," Ostro says. |
| www.findarticles.com /p/articles/mi_m1200/is_n22_v136/ai_8170441 |
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