Out of the Freezer

Collecting meteorites in Antarctica with ANSMET (image Linda Martel, ANSMET)

It is an astonishing fact that of the nearly 42,000 officially recognised meteorites logged on the Meteoritical Society database just over 29,000 were collected in Antarctica. That means that close to 70% of the worlds classified meteorites come from the most remote and inhospitable place on Earth. You won’t be surprised to learn that not a single one of these frozen extraterrestrial samples is a “fall”, i.e. a sample that was collected following its observed passage through the Earth’s atmosphere. They are all “finds” collected by well-organized national and international scientific expeditions.

This remarkable scientific endeavour started in December 1969 when 9 meteorites were located in the Yamato Mountains by members of the tenth Japanese Antarctic Research Expedition (JARE-10). A further small batch of meteorites was located in the same area in 1973. These discoveries led to a more systematic search in 1974 by JARE-15, which collected a further 663 samples. The United States recovery effort: ANSMET (Antarctic Search for Meteorites) got underway in 1976 with the collection of nine specimens from the Allan Hills, an area that lies close to the giant McMurdo research base. Collection activities have been undertaken by a wide range of other countries and groups including: Belgium, China, Italy, Korea and a European consortium known as EUROMET.

You might think that having already collected 29,000 specimens that would be enough (and in fact there a lot more in the pipeline that haven’t yet been classified). But it’s a bit like panning for gold. You have to trawl through a lot of specimens in order to find the rare and important samples.

And there have been some pretty amazing meteorites located in Antarctica.

The first meteorite to be recognised as having a lunar origin, Allan Hills A81005, was collected in Antarctica by ANSMET. We now have 146 lunar meteorites, of which 33 are Antarctic. The paired Antarctic meteorites GRA 06128 and GRA 06129 are unique samples from an unknown asteroid that produced granitic crust similar in composition to that found on the Earth. Auska 881394 is another unique sample collected by the Japanese. It was originally thought to be a member of the HED group and hence probably from the asteroid 4 Vesta. But further study, in particular oxygen isotope analysis, has revealed it to be a sample from a unique and as yet unidentified asteroid. Then there are the Martian meteorites collected in Antarctica. The most famous of these is Allan Hills 84001, which contains features that were interpreted as being evidence in favour of the existence of life on Mars in the distant past.

And compared to meteorites collected in hot desert regions, such as the Sahara or Oman, those from Antarctica tend to be much better preserved. Not surprising really, after being kept in the freezer all those years.

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