Change in climate could make meteorites disappear in Antarctic ice, says study

The icy plains of Antarctica are a magnet for meteorite hunters like Maria Valdes, a research scientist at the Field Museum of Natural History and the University of Chicago. About a thousand space rocks are found in the region each year. Its dark hue is easy to detect in the white expanse.

“Antarctica, an ice desert, provides an ideal setting 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 his work at the museum's Robert A. Pritzker Center for Meteorites and Polar Studies. The international team found five meteorites.

“We came across a huge brown rock isolated in the middle of an ice field. It was a little smaller than a bowling ball and quite heavy – 15 pounds,” she said in an 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 story about the solar system and how it was formed. But the climate crisis threatens this treasure trove of scientific information, according to a new study. Meteorites are disappearing into the ice, making them inaccessible to 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 was not involved in the latest research. “We have lost precious time capsules that contain clues about the history of our Solar System.”

As the Earth warms, around 5,000 meteorites could disappear from the surface of melting ice sheets each year, according to the study published Monday in Nature Climate Change magazine. To date, more than 48,000 meteorites have been discovered in Antarctica, representing about 60% of the specimens found globally.

How to find a meteorite

Meteorites, chunks of rock that fall from space through Earth's atmosphere at random, do not fall in an evenly dispersed pattern across the frozen continent. Concentrations arise in certain locations due to geography and weather patterns, explained Valdes.

Meteorites are particularly abundant 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 previously embedded in the ice. Wind-blown ice tends to appear blue compared to the surrounding surface snow.

“Over significant periods 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 blue ice rich in meteorites mainly by luck. However, to systematize the search, Veronica Tollenaar, a doctoral researcher at the Université Libre de Brussels in Belgium, and her colleagues used a machine learning algorithm to create a “treasure map” of zones likely to be rich in meteorites, based on factors such as surface temperature, surface slope, surface coverage and ice movement.

This research, published in January 2022 in Science Advances magazine, identified 600 zones and suggested that there are still 300,000 meteorites present on the surface of the ice cap. Valdes said in 2023 that she and her colleagues used the information to help decide on exactly where to look for the rocks during their expedition.

“Our experience indicates that, so far, the Tollenaar approach only works initially. Local parameters such as topography and wind directions that can redistribute meteorites from blue ice fields to local meteorite traps also have to be considered,” said Valdes.

In the new study, co-lead author Tollenaar and her team projected meteorite loss under different climate change scenarios by combining climate modeling with their 2022 work.

Meteorites can sink into ice even if temperatures are below zero degrees Celsius (32 Fahrenheit). The sun heats the dark rock, which absorbs solar radiation more easily because of its color, melting the surrounding ice. “With this heat, it can locally melt the ice and slowly disappear from the surface,” Tollenaar said.

Harry Zekollari, who was co-lead author with Tollenaar on the new study, said the cool surface temperature was one of four factors linked to a possible meteorite cluster.

“It's really important that it's cold and if your surface temperature starts to change, even if it goes from minus 12°C to minus 9°C, it's crossing a magical threshold where you're starting to lose meteorites,” said Zekollari, associate professor of glaciology at the Vrije Universiteit Brussel.

Under current policies, which the study said could result in warming of 2.6°C to 2.7°C above pre-industrial levels, researchers estimated that 28% to 30% of meteorites in Antarctica could fall. make inaccessible. Under a high emissions scenario, the estimate increased to 76%. Only at altitudes above 2,500 meters will meteorite losses be less than 50%, the study said.

Matthias van Ginneken, research associate at the Center for Astrophysics and Planetary Science at the University of Kent in the United Kingdom, said the work “made a lot of sense considering how global warming appears to be affecting Antarctica.”

However, van Ginneken, who was not involved in the study, said he wished the authors had talked more about the uncertainties in their model and conducted laboratory experiments to simulate how global warming affects meteorites, which would support the algorithm's results.

“It is certainly concerning, but there will still be thousands of meteorites to find per year,” he said in an email.

“The main concern is the logistical aspect of searching for meteorites in Antarctica, which is already difficult today due to Antarctica’s isolation. If the results of this study prove true, it will force scientists to explore new areas, potentially even further from the scientific foundations than are commonly explored. This would make this treasure even more inaccessible and therefore require more financing and logistical support.”

What We Learned From Antarctic Meteorites

Meteorites discovered in the southernmost regions of the planet have taught us a lot, said Kevin Righter, planetary scientist at the NASA Johnson Space Center in Houston (USA), in a commentary published with the research. He was not involved in the new study.

Scientists have recognized meteorites collected in the region in 1979 and 1981 as originating from the Moon, Righter noted. Before these discoveries, the only samples of the moon were from the Apollo and Luna landing sites. The meteorite samples resulted in a more random and comprehensive sampling of the entire lunar surface. Other meteorites have been connected to Mars.

“All this recent history of research indicates that with continued collecting, new types of meteorites will likely be found – including perhaps pieces of Mercury or Venus that may have been ejected from their surface after impacts.”

Righter, along with the study authors, called for collection efforts to be intensified and prioritized. “If meteorites are not collected quickly enough, they will be a lost resource for present and future planetary science,” he added.