The icy plains of Antarctica are a magnet for meteorite hunters such as Maria Valdes, a research scientist at the Field Museum of Natural History and the University of Chicago. Some 1,000 space rocks are found in the region each year. Their dark hue is easy to spot in the white expanse.
“Antarctica, a desert of ice, provides an ideal background for meteorite recovery — go to the right place, and any rock you find must have fallen from the sky,” said Valdes, who visited the region as part of an expedition team in late 2022 and early 2023 for her work at the museum’s Robert A. Pritzker Center for Meteoritics and Polar Studies. The international team found five meteorites.
“We stumbled across an enormous brown stone sitting by itself in the middle of an ice field. It was a little bit smaller than a bowling ball and quite heavy — 7.6 kg (about 17 pounds),” she said via email. “I had seen and handled so many meteorites in my career, but finding one yourself is such a different feeling.”
Formed from extraterrestrial bodies such as the moon, Mars or large asteroids, each meteorite tells a unique tale about the solar system and how it was formed. But the climate crisis threatens this trove of scientific information, according to a new study. Meteorites are disappearing into the ice, putting them out of the reach of scientists.
“As the climate continues to warm, Antarctic rocks are sinking into the ice at an increasing rate. Over time, this will make many meteorites inaccessible to scientists,” said Valdes, who wasn’t involved in the latest research. “We lose precious time capsules that hold clues to the history of our Solar System.”
As Earth warms, about 5,000 meteorites could disappear from the surface of melting ice sheets every year, according to the study published Monday in the journal Nature Climate Change. To date, more than 48,000 meteorites have been discovered in Antarctica, accounting for about 60% of specimens found globally.
How to find a meteorite
Meteorites, lumps of rock that fall from space through Earth’s atmosphere randomly, do not fall in an evenly scattered pattern across the frozen continent. Concentrations emerge in certain locations because of geography and weather patterns, Valdes explained.
Meteorites are particularly plentiful in blue ice fields. In these areas, a combination of ice flow processes and local weather conditions remove layers of snow and ice from the surface, exposing meteorites that were once embedded in the ice. The windblown ice tends to look blue compared with the surrounding surface snow.
“Over significant stretches of time (tens or hundreds of thousands of years) phenomenal concentrations of meteorites can develop, as high as 1 per square meter in some locations,” she said.
Researchers have identified areas of meteorite-rich blue ice mostly by luck. However, to systematize the search, Veronica Tollenaar, a doctoral researcher at Université Libre de Bruxelles in Belgium, and her colleagues used a machine-learning algorithm to create a “treasure map” of probable meteorite-rich zones, based on factors including surface temperature, surface slope, surface cover and ice flow movement.
That research, published in January 2022 in the journal Science Advances, identified 600 zones and suggested that 300,000 meteorites are still present at the surface of the ice sheet. Valdes said in 2023 she and her colleagues used the information to help inform their decision on exactly where to search during their expedition.
“Our experience … indicates that so far, Tollenaar’s approach only works to a first order. Local parameters such as topography and wind directions that can redistribute meteorites from blue ice fields into local meteorite traps have to be considered as well,” Valdes said.
In the new study, co-lead author Tollenaar and her team projected the loss of meteorites under different climate change scenarios by combining climate modeling with their work from the 2022 paper.
The meteorites can sink into the ice even if temperatures are below zero degrees Celsius (32 Fahrenheit). The sun heats up the dark rock, which absorbs solar radiation more easily because of its color, which melts the surrounding ice. “With that heat, it can locally melt the ice and slowly disappear from the surface,” Tollenaar said.
Harry Zekollari, who was co-lead author along with Tollenaar on the new study, said that cold surface temperature was one of four factors linked to a potential meteorite cluster.
“It’s really important that it’s cold and if your surface temperature starts changing, even if it’s going from minus 12 C to minus 9 C, it’s crossing a magic threshold where you’re starting to lose meteorites,” said Zekollari, an associate professor of glaciology at the Vrije Universiteit Brussel.
Under current policies, which the study said may result in a warming of 2.6 degrees Celsius to 2.7 degrees Celsius (4.7 F to 4.9 F) above preindustrial levels, the researchers estimated that 28% to 30% of the meteorites in Antarctica could become inaccessible. Under a high-emission scenario, the estimate increased to 76%. Only at elevations above 2,500 meters (8,202 feet) will meteorites losses be less than 50%, the study said.
Matthias van Ginneken, a research associate at the University of Kent’s Centre for Astrophysics and Planetary Science in the UK, said the work “made a lot of sense considering how global warming seems to affect Antarctica.”
However, van Ginneken, who wasn’t involved in the study, said he wished the authors had talked more about uncertainties in their model and conducted lab experiments to simulate how global warming affects meteorites, which would support the results of the algorithm.
“It is certainly worrying, but there will still be thousands of meteorites to find per year,” he said via email.
“The main worry is the logistical aspect of searching for Antarctica meteorites, which is already difficult today due to the remoteness of Antarctica. Should the results of this study prove to be true, it will force scientists to explore new areas, potentially even further away from scientific bases than those that are commonly explored. It would make this treasure trove even more inaccessible and, thus, necessitate more funding and logistical support.”
What we’ve learned from Antarctic meteorites
Meteorites discovered in the southernmost reaches of the planet have taught us a lot, said Kevin Righter, a planetary scientist at NASA Johnson Space Center in Houston in a commentary published alongside the research. He was not involved in the new study.
Scientists recognized meteorites collected in the region in 1979 and 1981 as originating from the moon, Righter noted. Before these finds, the only samples from the moon were from the Apollo and Luna landing sites. The meteorite samples have resulted in a more random and comprehensive sampling of the entire lunar surface. Other meteorites have been connected to Mars.
“All of this recent research history indicates that with continued collection, new meteorite types are likely to be found — including perhaps pieces of Mercury or Venus that might have been ejected from their surface following impacts.”
Righter, along with the study authors, called for collection efforts to be ramped up and prioritized. “If meteorites are not collected quickly enough, they will be a lost resource for present and future planetary science,” he added.