Close Encounters with Asteroids and Comets: New Insights from Dawn to Galileo

The recent visits, impacts, sampling and close-up photography of asteroids and comets have revealed complex minor planetary bodies that are of great scientific and economic interest. Prior to these recent results, we were dependent on information gained by examining meteorites that have fallen to earth and our telescopic and radar observations of these objects in space. The Japan Aerospace Exploration Agency’s (JAXA) Hayabusa mission, launched in 2003, returned to earth in June, 2010 with the first samples from an extraterrestrial body since the Apollo missions. The most immediate impact of these samples was to confirm that the Hayabusa’s samples of Asteroid Itokawa were similar in composition to LL Chondrites, a common stony meteorite found on earth, validating the more than 40,000 meteorite finds on earth as being representative samples of objects in space. The NASA Deep Impact mission provided a different body of information for Comet Tempel-1 that included close up photography and spectroscopic analysis of a plume created by a designed impact into Comet Tempel-1. The NASA Dawn mission, launched in 2007, is now returning exceptional high resolution imagery of asteroid Vesta from the Main Asteroid Belt, and will proceed to the minor planet Ceres, arriving July, 2015.

This unprecedented body of data on the physical and chemical composition of asteroids and comets is as significant as the return of lunar samples by the Apollo program. The thermal and chemical evolution reflected in the initial results of the Hayabusa’s samples of the Itokawa Asteroid indicated a complex thermal, radiation and impact history. These data provide hints on the early history of the solar system, the dynamic evolution of asteroids and the internal structure and composition of comets. These minor planetary bodies have much to contribute to our knowledge of the solar system and should not be neglected in the planning of future missions.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California