Antarctic Meteorite Program

The exploration of the Antarctic and the development of space science have experienced parallel growth over the past several decades. These capabilities have been combined to make the recovery of meteorite specimens from Antarctica both scientifically important and feasible. Meteorites are important scientifically because they were formed during the earliest history of the solar system (some may even contain pre-solar system remains) and can provide information about the physical and chemical makeup of the solar system.

In 1969, Japanese scientists first discovered concentrations of meteorites in the Antarctic. The meteorites, most of which have fallen to Earth during the past million years, have been preserved in ice and concentrated in areas characterized by stagnant "blue ice." Since this accidental discovery teams of scientists from Japan, the US, and Europe have gone to Antarctica every year to search for meteorites. More than 16,000 pieces of meteorites have been recovered in Antarctica, more than doubling the number of individual meteorites available for scientific study. Even more significant is the high percentage of rare meteorites such as lunar and martian specimens. This makes the Antarctic meteorite collection particularly interesting.

The US Antarctic Meteorite Program is a collaborative effort among three government agencies; the National Science Foundation (NSF), the National Aeronautics and Space Administration (NASA), and the Smithsonian Institution. The NSF, with decades of experience in exploring this harsh environment, provides support for field research and collection. NASA and the Smithsonian Institution, as experts in curation of respectiviely lunar samples and all geologic specimens, provide for the classification, storage and distribution of Antarctic meteorites. All three agencies sponsor research on these valuable specimens.

In the Apollo program, spacecraft from Earth brought men to the Moon to collect samples from another planet of our solar system. In an environment nearly as harsh, helicopters are used to airlift scientists to Antarctic icefields. Their objective is to collect meteorites - fragments of asteroids, comets, or other planets - that have been preserved in or on the ice after their fall to Earth. While the Moon rocks gave direct evidence of the origin and history of the Moon, part of the Antarctic meteorite puzzle is to trace the paths of these fragments from outer space so that their planetary origins can be determined.

Although supported by modern equipment, the Antarctic meteorite search requires that men and women work under conditions of severe cold and bad weather in isolated camps. Meteorites are collected by persons on foot and snowmobile who scour areas of snow-free "blue ice." The meteorites are found on the surface, where they are detected as pieces as small as 1 centimeter in diameter.

The meteorites lie on the surface of the ice, thus show less weathering than a similar meteorite found in temperate climates; in addition, because of the absence of industrial pollutants, they remain relatively uncontaminated. Extra efforts are made to document each sample, to provide clean containers, and to maintain the samples in a cold environment until the adhering snow and ice can be removed in the laboratory by sublimation.

Most meteorites preserve the original fusion crust, a thin melted zone formed by intense surface heating as the meteorite passed through the atmosphere. Others, not as strong, have been broken during transportation through the ice and may be recovered as small fragments. The largest and weakest meteorites broke into many pieces as they passed through the atmosphere and fell to the Earth as showers of fragments.

When a meteorite is found, scientists use the numbering device that was originally used by Apollo astronauts in collecting and documenting lunar rocks. It provides a convenient marker as well as a gray scale for photographic calibration.

The Antarctic meteorites have been concentrated in certain location, but the mechanism of concentration is not completely understood. A leading hypothesis is that the meteorites fell on snowfields where ice thickness increases, flowed toward the edge of the Antarctic Continent, and became exposed where the iceflow is impeded by obstacles and where the ice is ablated.



The wind continually ablates the ice surface in the areas of meteorite concentration, removing ice by sublimation and mechanical abrasion. In order to measure the amount of ablation, a series of stakes has been emplaced and accurately surveyed with respect to a base station on rock outcrops. Ablation rates have been as high as 10 centimeters per year.

To determine the age of the ice that encased the meteorites (that is, when it was first deposited as snow), cores of ice are analyzed in the laboratory. New methods are being developed to determine the age of ice. Since some of the ice is believed to have resided within the ice sheet for more than a million years, analysis of ice samples may provide information on the rate of motion of the meteorite along a trajectory within the ice sheet.

Although many of the meteorites fell tens of thousands to a million years ago, they are still remarkably fresh and uncontaminated, having been preserved within the ice. In handling the meteorites, precautions are taken to preserve them from degradation and contamination. They are taken to the Meteorite Curation Facility at the NASA Johnson Space Center (JSC), where they are processed in the controlled atmosphere cabinets formerly used to process lunar samples. The water- and oxygen- free nitrogen gas in the cabinets keeps the meteorites from oxidation (rusting) and from contamination by environmental pollutants such as organic compounds, heavy metals, and salts, which could reduce the scientific value of the specimens. At JSC, the meteorite samples are chipped, sawed, weighed, and photographed in nitrogen cabinets without exposure to the air or to any cooling fluids.

Valuable Scientific information is being gained from this program of collecting and studying meteorites.

• New types of meteorites and rare meteorites have been found.
• The larger collection of meteorites allows a better understanding of the abundance of meteorite types in the solar system.
• The old terrestrial age of some meteorites allows a look back into time to see what the abundances were millions of years ago and to study the behavior of the Sun, which implanted particles in these meteorites during their cosmic journey but not after they fell to Earth.
• The cleanliness of the samples allows studies that previously were difficult or impossible with available samples.
• New information may be obtained about the flow of ice in the Antarctic ice sheet.

The Antarctic meteorite program is a cooperative international effort that is providing important new scientific data on our solar system. The use of modern Antarctic equipment and technology and the sample handling and study techniques developed through the lunar sample study program have made separate but crucial contributions to the success of the program.