spacetoday.net: Comet dust composition similar to asteroids

Posted: Fri, Jan 25, 2008, 7:25 AM ET (1225 GMT)
Much to their surprise, planetary scientists have found that comet dust collected by a NASA spacecraft closely resembles materials found in asteroids. In a paper published in this week's issue of the journal Science, researchers found that dust collected from comet Wild 2 by NASA's Stardust spacecraft has a composition that more closely resembles chondritic meteorites from the asteroid belt. Scientists has expected the comet dust to contain relatively primitive materials dating back to the formation of the solar system, but instead found compounds that would only have formed much closer to the Sun. The results suggest that the comet actually formed relative close to the Sun and was later ejected into the outer solar system, rather than initially forming in the outer solar system as previously believed.