Nearly 50,000 meteorites have been found in Antarctica and hundreds of thousands more could be recoverable. Each one tells a story of the solar system’s evolution—the first lunar rock found on the icy continent showed that material from celestial objects larger than asteroids could end up on Earth.
Finding them isn’t easy, though, and requires teams to visit remote areas with no guarantee that any will be visible. Currently, scientists find around 1,000 meteorites in Antarctica each year. But a new study published in Nature Climate Change estimates that about 5,000 are buried out of sight every year due to warming temperatures.
To estimate this change, scientists developed a model that identifies where meteorites might surface. They based those chances on factors such as snow cover, surface temperatures, how fast the ice flows, and the steepness of the terrain. Then, they ran simulations under different warming scenarios and found that meteorites sink out of sight below the ice as temperatures rise.
“This is a bit of an unexpected impact of climate change,” says co-lead author Harry Zekollari, a glaciologist at the Vrije Universiteit Brussel. “These places are below freezing, yet we are still profoundly affecting a very important archive of the solar system.”
The challenging hunt for meteorites
Currently, scientists find about 1,000 meteorites in Antarctica every year. But changing weather conditions may hide thousands more beneath the ice.
Photograph by Cindy Evans, NASA
The majority of Antarctic meteorites have been recovered near the base of mountains or outcrops where ice, which normally flows to lower elevations, is forced upwards. There, strong winds brush away snow, exposing ice that’s so old it appears as a bright, vivid blue. Instead of melting, some of the ice also changes directly to water vapor, helping to expose meteorites that otherwise would remain buried.
Meteorites at the surface can quickly disappear, though. When temperatures are well below freezing, the rocks can absorb enough of the sun’s heat to melt the ice, causing them to sink.
Then, subsequent refreezing renders the meteorites stranded in their melt-pockets, tucked out of sight.
“It’s very difficult to develop methods to find these meteorites,” says co-lead author Veronica Tollenaar, a glaciologist at the Université libre de Bruxelles. “That’s why we speak of meteorites being unrecoverable.”
Based on the expected warming under current policies, the team’s computer simulations showed that about one-third of visible meteorites will sink under the ice before the end of this century. This translates to a total loss of between 80,000 and 250,000 meteorites.
Losing the history of the solar system
The list of Antarctic meteorites also includes samples from Mars: The most famous, ALH 84001 contains minerals that support evidence that the Red Planet was warm and had water on its surface billions of years ago.
The ice sheet’s meteorites also contain materials that were once “free-floating bits of dust in the early solar system,” says Sara Russell, a meteorite expert at the Natural History Museum in London.
These rocks often contain minerals that have been altered by water that melted from ice they once contained in space. By studying these altered rocks, researchers can study how asteroids colliding with Earth may have supplied the water molecules that formed our planet’s oceans billions of years ago.
Meteorites also provide information about other processes that may have taken place early on; for example, whether Jupiter’s immense gravity prevented materials from different regions of the solar system from mixing together.
Antarctic meteorites are also the least weathered space rocks on Earth. The cold, dry environment helps preserve them. As a result, scientists are confident that their materials represent conditions that existed in the solar system when they formed.
The samples also include unique rocks that haven’t been found elsewhere, says Russell.
These could be from new types of asteroids or pieces from familiar kinds that haven’t made it to Earth before, showing how diverse the population of such celestial objects are.
The race to find Antarctic meteorites
Finding more meteorites before they disappear is not an easy endeavour, though, and ultimately requires “getting some boots on the ice to go looking for them,” says Ralph Harvey, a planetary scientist at Case Western Reserve University.
Harvey adds that “the type of work the researchers of the new study are doing is perfect for extending the limits of where meteorites might be found and showing how these places may be changing.”
Zekollari says that certain areas where the study predicts meteorites will disappear more quickly should be prioritized.
“We don’t have a lot of time,” adds Tollenaar. “We need to go with more people to more places to recover the relics.”
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