Terrestrial Ages of Four Allan Hills Meteorites: Consequences for Antarctic Ice

Advances in Cosmochemistry Enabled by Antarctic Meteorites

At present, meteorites collected in Antarctica dominate the total number of the world's known meteorites. We focus here on the scientific advances in cosmochemistry and planetary science that have been enabled by access to, and investigations of, these Antarctic meteorites. A meteorite recovered during one of the earliest field seasons of systematic searches, Elephant Moraine (EET) A79001, was identified as having originated on Mars based on the composition of gases released from shock melt pockets in this rock. Subsequently, the first lunar meteorite, Allan Hills (ALH) 81005, was also recovered from the Antarctic. Since then, many more meteorites belonging to these two classes of planetary meteorites, as well as other previously rare or unknown classes of meteorites (particularly primitive chondrites and achondrites), have been recovered from Antarctica. Studies of these samples are providing unique insights into the origin and evolution of the Solar System and planetary bodies.

Catch a falling star: meteorites and old ice

A model for the process of meteorite concentration in blue ice regions of the Antarctic ice sheet is proposed based on data from near the Allan Hills and the assumptions that both meteorite influx and glacial flow have been constant. The meteorite influx is calculated to be 60 x 10(-6) kilogram per square kilometer per year, and the age of the exposed ice to be 0 to 600,000 years, varying with distance from the Allan Hills. These results are in line with other estimates of influx rate and with measurements of the terrestrial ages of the meteorites, providing support for the assumption of steady flow and meteorite influx. This may be the oldest sequence of ice in stratigraphic order yet discovered, and the results imply that this part of the east Antarctic ice sheet has been approximately steady during this time interval.

Amino Acids in an Antarctic Carbonaceous Chondrite

Amino acids have been found in aqueous extracts of a C2 carbonaceous chondrite recovered from Antarctica. The composition of the amino acids strongly suggests that they have a meteoritic origin. Comparison of these results with those obtained with other C2 chondrites supports the view that Antarctic meteorites have not been significantly altered by terrestrial processes since their fall.