We’ve read news stories about researchers studying ice cores pulled up hundreds of feet through ice sheets, sediment samples drilled from ancient lakebeds, and microfossils of plankton that once surfed now-freezing ocean surfaces. Another even more unusual product is boxed up in Antarctica and sent to waiting labs—rocks from outer space.

According to the Antarctic Sun web site, for over 30 years field researchers have found and boxed some 17,500 rocks in their frozen state for shipment to the Antarctic Meteorite Laboratory at the Johnson Space Center in Houston, Texas. There the curator team thaws the rocks in a sterile dry nitrogen cabinet and begins to categorize them. (The samples are kept frozen until the team is ready to analyze them because any iron content might rust in a nonfrozen state.)

The meteorites are collected by National Science Foundation-funded teams operating out of the McMurdo and South Pole Stations. The teams work in dangerous, harsh conditions as they walk or ride snowmobiles to scan the ice surface for meteorites that may be as small as 1 centimeter in diameter. In spite of that, the teams typically send a few hundred samples each season. One season, teams collected more than 1,300 samples. In glacial moraines, the teams must be able to distinguish between earth rocks and meteorites.

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. As many meteorites have been recovered in Antarctica as in the rest of the world combined.

Although the continent has already yielded so many meteorites, Ralph Harvey, who heads the Antarctic Search for Meteorites (ANSMET) field program, says it’s still important to bring back more specimens. “There’s always the potential for something that’s going to change the whole way we see the solar system.”

Recently, rocks found at the Graves Nunatak ice field were unlike anything found before. Early speculation on their origin focused on planetary bodies like Venus or Jupiter’s moon Io. The composition of the light-colored rocks has similarities to the earth’s crust, which has implications for how some asteroids form and evolve.

The large and growing collection of meteorites has fostered a large amount of research leading to a better understanding of the early solar system, and the origin of asteroids and comets.