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Project Progress

Kress and Brownlee, in collaboration with George Cody, have investigated the thermal alteration of organic material entering the atmosphere in small extraterrestrial particles. An interesting aspect of this process is that even the most severely heated particles eject sublimed compounds that survive. This work has involved the analysis of organics released from pulse heated carbonaceous chondrites under conditions that simulate the atmospheric entry of 200-µm particles. Most of the Earth’s 30,000 tons of annually accreted material arrives in comet and asteroid particles of this size. This work is underway but will provide a good estimate of the nature and amounts of simple organic compounds accreted by habitable zone planets.

Matrajt and Brownlee worked on a variety of problems related to the nature and abundance of organic materials in small extraterrestrial materials that enter the Earth’s atmosphere. They have developed methods for mounting and handing micrometeorites for organic studies by electron energy loss spectroscopy (EELS) in the transmission electron microscope. This work has been very successful but a challenge due to multiple sources of contamination and substrate interference. This work is yielding direct information on the fine scale distribution and composition of organic materials in small cometary and asteroidal particles. Working with S. Pizzarello and S. Taylor , they determined the α -aminoisobutyric acid (AIB) amino acid content of micrometeorites recovered from pre-industrial ice at the South Pole. Working with L. Leshin (Arizona State University (ASU)) and M. Genge (Open University) they are studying the organic, mineralogical, and oxygen isotopic composition of a large suite of unmelted micrometeorites >100 µm collected from South Pole ice. They are also comparing these materials with those that form meteorites, and have found that carbon-rich bodies are the dominant source of particles <1 mm diameter.

Brownlee and his Stardust collaborators made a close flyby of comet Wild 2 on January 2, 2004 , providing an unprecedented wealth of information on a Kuiper belt comet, a class of body that delivers organic materials and water to habitable zone planets. This work showed that comets are considerably different than asteroids and other solar system bodies. See figure 2.

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Figure 2 Unavailable