Meteorites

Meteorite from Mars For some time now, scientists have been traveling by snowmobile along the margins of the polar plateau west of the Transantarctic Mountains. They are searching for meteorites--material that has impacted the Earth from outer space. Prior to 1969, however, when nine meteorites were found almost by accident, by the Japanese in the Yamato Mountains near their Syowa Base, only six meteorites had been found in Antarctica the first in 1912. In fact, prior to 1969, only about 2100 distinct (individual, not fragments) meteorites were known worldwide, with only five to ten new ones being recovered annually from the rest of the Earth.

Space Rocks
  • Meteorites are a major source of information about the early history of our solar system.
  • Most of our knowledge about meteorites comes from analysis of those found in Antarctica, which acts as a huge meteorite collector and preserver.
  • The first Antarctic meteorite was found by Australians in 1912, but serious collecting did not begin until 1969.
  • Since then, more than 10,000 have been discovered, mainly by Japanese and US scientists.

Antarctica is a unique collecting ground for the recovery of large numbers of meteorites. It has been determined that meteorites striking the vast ice sheet are better preserved than anywhere else in the world, through their burial in the ice for periods ranging from 1000 to 700,000 years (dated by isotope measurements). This is relatively old when considering the 200 year old age identified for meteorites found in more humid and less protected regions of the Earth. The meteorites are believed to move downward within the ice, following its flow lines toward the continental margins, where they are either discharged unnoticed into the sea or are captured in ice where they stagnate against a resistant mountain barrier, There the flow path in the ice brings them to the surface, where they are now being found in large numbers.

Among the most unexpected finds was a meteorite fragment whose mineral content identified it as coming from the Moon, presumably a result of "splatter" created by the impact on the lunar surface of a large asteroid. For such a rock to travel to the Earth from the Moon would require an escape velocity from the Moon accelerated to about 8,750 kilometers per hour. Even more incredible is the meteorite fragments found from Mars--the escape velocity from that planet would have to be about 18,000 kilometers per hour. These specimens are at the center of the controversy about possible evidence of microbial life on early Mars.

scientists recording a meteor findMeteorite studies are a significant part of space science because the specimens include the oldest materials of the Solar System available for research. They provide identifiable records of certain solar and galactic effects, and they yield data that are otherwise not obtainable--about the origin, evolution, and composition of the Sun, the Earth, and other planets, satellites, and asteroids. The techniques and ideas developed in the collection, study, and preservation of meteorite specimens are transferable to the studies of lunar samples, and have thereby yielded large amounts of information about the Moon and Sun, and the Solar System.

Why Are So Many Meteorites Found in Antarctica?
  • They are easily seen against the ice.
  • They are quickly covered by snow and eventually frozen solidly into the icepack, protecting them from rusting, weathering and corroding.
  • The ice sheet both transports and concentrates the meteorites as it slips off the plateaus and churns against the mountains.
  • The meteorites are generally found in the 'blue ice' areas of Antarctica, which are expanses of old ice kept free of snow by constant winds.
  • Areas of sublimating (evaporating) ice allow the meteorites to gradually 'rise' to the surface.
Did You Know?
  • finding a meteor on the ice sheetToday, there are consortiums of many nations whose members are busy searching the ice sheet and picking up these samples from outer space.
  • Most of the fun may be in the finding, but the science is taken seriously to the point of keeping the meteorites frozen until they can be returned to a "clean lab," where they are treated with the same care that was given to the samples returned from the moon.
  • Some of them have been found to be unlike any others found elsewhere on earth.
  • Not entirely without reason, the collectors have taken to referring to a find as "a poor man's space probe."