Magazine article Science News

Asteroid Studies Reveal New Puzzles. (Astronomy)

Magazine article Science News

Asteroid Studies Reveal New Puzzles. (Astronomy)

Article excerpt

Nearly half the largest rocks strewn across the asteroid 433 Eros come from material blasted from a single impact, a new analysis reveals. A detailed study of Eros--the first asteroid that a spacecraft has landed on (SN: 7/21/01, p. 38)--reveals that among 6,760 rocks larger than 15 meters across, 44 percent originated from what is now a crater called Shoemaker. This 7.6-kilometer-wide depression lies at one end of the asteroid.

Peter C. Thomas of Cornell University and his colleagues found that the placement of the large rocks matched the predicted paths of debris ejected by the impact that created the Shoemaker crater. Although some of the debris "went straight up and straight down," other chunks traveled as far as two-thirds of the way around the rotating, 34-km-long asteroid, Thomas notes.

He and his collaborators, who include Joseph Veverka of Cornell and Mark S. Robinson of Northwestern University in Evanston, Ill., describe several new findings about Eros in a trio of reports in the Sept. 27 NATURE.

One puzzle, notes Thomas, is that debris from two other large craters, Himeros and Psyche, don't seem to have made a significant contribution to the larger rocks observed on the asteroid's surface. Both craters ate older than Shoemaker, and it could be that rocky material excavated by these impacts has since been buried or eroded, says Thomas. Alternatively, because of differences in rock strength and composition at various locations, the impacts that gouged Himeros and Psyche may simply have made fewer large rocks.

Detailed maps showing features on Eros as small as 1. …

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