HR: 1340h
AN: P33A-0996    [Abstracts]
TI: Determing the Possible Building Blocks of the Terrestrial Planets
AU: * Burbine, T H
EM: tburbine@lepvax.gsfc.nasa.gov
AF: Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 United States
AB: One of the pioneers in the study of chondrites and planetary formation is John Wood. John has worked on a wide variety of subjects such as the condensation of chondritic material in the solar nebula and the heating sources that formed differentiated bodies. One unsolved question concerning planetary formation is exactly what material did the planets and asteroids form from. All the bodies in our solar system are believed to have formed out of material from the solar nebula. Chondritic meteorites appear to sample this primitive material. Detailed studies of the possible building blocks of the terrestrial planets and asteroids require samples that can be used to estimate the bulk chemistry of these planetary bodies. It appears very difficult to impossible to build the terrestrial planets out of a single type of chondritic meteorite. To try to determine possible building blocks of the terrestrial planets and asteroids, a computer program has been developed that inputs average oxygen isotopic values as well as average bulk chemical data for each chondritic group. Aggregate oxygen isotopic and bulk chemical compositions for every possible combination of these meteorites at mass increments of 5 percent were computed. Elements and compounds were combined linearly except for the oxygen isotopic values, which were weighted by the oxygen content of each meteorite. Redox reactions were used to determine the FeO content of each matching combination. Over 225 million combinations of the thirteen meteorite groups are produced. The bulk oxygen isotopic and chemical chemistries of the combinations can then be compared to those of any planet or asteroid. This modeling shows that it is extremely difficult to form the Earth out of known chondrites, but much easier to form Mars. This method will be used to determine possible chondritic precursors of differentiated asteroids such as the angrite and the basaltic achondrite parent bodies. Samples from Mercury and Venus are needed to determine possible building blocks of these planets.
DE: 6225 Mars
DE: 1060 Planetary geochemistry (5405, 5410, 5704, 5709, 6005, 6008)
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting