Antarctic meteorites

Allan Hills, Antarctica

Allan Hills, in Eastern Antarctica, forms a barrier to the flow of ice into the Ross Sea. This is the region where an American party first searched in 1976 following spectacular earlier discoveries by the Japanese in the Yamato (Queen Fabiola) Mountain area on the other side of the continent. In the Allan Hills area, rocks actually protrude above the ice to form the barrier, but in other areas it has been found that buried topography can cause an upward movement of ice, leading to ablation and the exposure of meteorites. American teams have now located meteorites at more than 20 localities in Antarctica. Most of these are situated to the west or south of the Ross Sea and Ross Ice Shelf. (Courtsey Dr. Ursual Marvin, Smithsonian Astrophysical Laboratory, Cambridge, Ma., U.S.A.)

Concentration of meteorites

This slide shows the mechanism of concentration of meteorites in Antarctica originally proposed by Kezio Yanai of the Japanese National Institute of Polar Research in Tokyo. Meteorites falling on the ice cap in regions of substantial accumulation are gradually buried deeper in the ice and are carried with it as it flows toward lower ground. Although much of the ice (and the meteorites it contains) ends up in the sea, some of it comes up against natural barriers, such as a range of hills or mountains. Here the ice is forced upward. Ablation from katabatic winds continually removes ice from the upper surface and leaves the meteorites it contained, exhumed on the surface. Such dense, compact ice with no snow cover is a distinct pale blue colour. (Courtesy Dr. Ursula Marvin, Smithsonian Astrophysical Laboratory, Cambridge, Ma., U.S.A)

Meteorite exposed in ice

This slide shows a small meteorite still embedded in Antarctica blue ice. Note that an identification number ('439') has been painted on the ice before it was photographed. The meteorite is then chipped out of the ice and taken in an inert atmosphere and still frozen to a facility at the Johnson Space Centre in Houston, where it is finally stored under a program run jointly by NASA and the Smithsonian. 'Terrestrial' isotopic ages of these Antarctic meteorites offer a means of dating the ice sheet. Meteorites recovered from the ice have been referred to as 'fossil' meteorites and distinguished as a group from those found elsewhere on Earth. (Courtesy Dr. Ursula Marvin, Smithsonian Astrophysical Laboratory, Cambridge, Ma., U.S.A.)

More information on Antarctic meteorites is available from Johnson Space Center

MIAC Slide Group and Michael Higgins