Constraints on the Formation Age of Cometary Material from the NASA Stardust Mission

Abstract

Sun Stuff Comets are thought to be remnants of the Sun's protoplanetary disk; hence, they hold important clues to the processes that originated the solar system. Matzel et al. (p. 483 , published online 25 February) present Al-Mg isotope data on a refractory particle recovered from comet Wild 2 by the NASA Stardust mission. The lack of evidence for the extinct radiogenic isotope 26 Al implies that this particle crystallized 1.7 million years after the formation of the oldest solar system solids. This observation, in turn, requires that material formed near the Sun was transported to the outer reaches of the solar system and incorporated into comets over a period of at least two million years.