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Ages and isotopes of particles from Comet P/Wild-2 (Funded by NASA)

The project is in collaboration with Prof. Stein Jacobsen. The main objective of this project is to measure selected isotopic and elemental compositions of particles returned from Comet P/Wild-2 and compare the results with other known samples of extraterrestrial materials in order to (1) determine the extent to which the P/Wild-2 materials are similar to or distinct from any known type of meteoritic components and (2) estimate the proportions of presolar and nebular materials in P/Wild-2

Specifically we will make the following measurements

87Rb-86Rb and 40K-40Ar ages: If comets are prisitne solar system materials that have not undergone any processing, then the Rb-Sr and K-Ar ages are likely to date the start of the solar system or even pre-data the age of the solar system if presolar grains have been preserved without significant thermal processing. The latter is certainly a possibility given that D/H ratio in some IDPs, believed to be derived from comets, approach ratios observed in molecular colouds. However, if comets have undergone collisional processing then the Rb-Sr and K-Ar ages are likely to be much younger than the solar system age. Therefore, these ages are going to be critical in establishing teh importance of collisional processing in comets.

Noble gas abundacne patterns and isotopic ratios, with special emphasis in He, Ne, and Ar: A number of planetary accretion models have suggested cometary noble gases as important contributors of Earth atmosphere (e.g., Owen and Bar-Nun, 1995a.b; Harper and Jacobsen, 1996). For example, Harper and Jacobsen proposed that the light noble gases in the solid Earth were primarily from the accretion of planetesimals with a meteoritic noble gas pattern and the atmosphere from a late veneer of volatile rich objects, such as comets. However, many of the proposed models are currently not testable as the noble gas composition of comets is unknown.

We are currently in the process of fine tuning our measrument techniques by using micron-sized fragments from Murchison. The actual measurments on the comet dust will commence once Stardust returns back to Earth in January 2006. To learn more about Stardust and the goals of the mission visit the Stardust web site.



Artist's rendition of the comet sample return spacecraft, Stardust.