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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 1,000 space rocks are found in the region each year. Its dark color is easy to see in the white field.
“Antarctica, an ice desert, provides a great backdrop 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 ‘tour team late. 2022 and early 2023 for her work at the museum’s Robert A. Pritzker Center for Meteorology and Polar Studies. The international team found five meteorites.
“We came across a huge brown stone sitting by itself in the middle of an ice field. It was slightly smaller than a bowling ball and quite heavy – 7.6 kg (about 17 pounds),” she said via email. “I’ve seen and handled so many meteorites in my career, but it’s a different feeling to find one for yourself.”
Each meteorite tells a unique story about the solar system and how it was formed, made from extraterrestrial bodies such as the moon, Mars or large asteroids. But this scientific knowledge threatens the climate crisis, 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 lose precious time capsules that hold clues to the history of our Solar System.”
As the Earth warms, about 5,000 meteorites could leave the surface of the melting ice sheets each year, according to the study published Monday in the journal Nature Climate Change. To date, more than 48,000 meteorites have been found in Antarctica, representing approximately 60% of the specimens found worldwide.
How to find a meteorite
Meteorites, lumps of rock that fall from space through the Earth’s atmosphere at random, do not appear in an evenly distributed pattern across the frozen continent. Concentrations occur in certain locations due to geography and weather patterns, Valdes explained.
Meteorites are especially abundant in blue ice areas. 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. Windblown ice tends to appear blue compared to the surrounding surface snow.
“Over significant periods of time (thousands or thousands of years) spectacular concentrations of meteorites can develop as high as 1 per square meter in some places,” she said.
Researchers have identified areas of meteorite-rich blue ice mostly by luck. To systematize the search, however, Veronica Tollenaar, a doctoral researcher at Université Libre de Bruxelles in Belgium, and her colleagues used a machine learning algorithm to create a “cache map” of potentially 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 on the surface of the ice sheet. Valdes said in 2023 that she and her colleagues used the information to help them decide exactly where to search during their trip.
“Our experience … suggests that Tollenaar’s approach so far only works of the first order. Local parameters such as topography and wind direction must also be considered which can redistribute meteorites from blue ice fields to local meteorite traps,” said Valdes.
In the new study, co-author Tollenaar and her team predicted the loss of meteorites under various climate change scenarios by combining climate modeling with their work from the 2022 paper.
The meteorites can penetrate the ice even if the temperature is below zero degrees Celsius (32 degrees Fahrenheit). The sun heats up the dark rock, which absorbs solar radiation more easily due to its color, which melts the surrounding ice. “With that heat, the ice can melt locally and it slowly disappears from the surface,” Tollenaar said.
Harry Zekollari, who was co-lead author with Tollenaar on the new study, said cold surface temperatures were one of four factors associated with a possible meteorite cluster.
“It’s really important that it’s cold and if your surface temperature starts to change, even if it’s going from minus 12 C to minus 9 C, it’s crossing a magic threshold where you’re starting to get lose,” said Zekollari, an associate professor of glaciology at Vrije University in Brussels.
According to current policies, which the study said could result in warming of 2.6 degrees Celsius to 2.7 degrees Celsius (4.7 F to 4.9 F) above pre-industrial levels, the researchers estimated that 28% to 30% of the meteorites could in Antarctica being inaccessible. Under a high emissions scenario, the estimate increased to 76%. Only at altitudes above 2,500 meters (8,202 feet) will meteorite losses be less than 50%, the study said.
Matthias van Ginneken, a research associate at the University of Kent’s Center for Astrophysics and Planetarium in the United Kingdom, said the work “made a lot of sense when Antarctica seems to be affected by global warming.”
However, van Ginneken, who was not involved in the study, said he wished the authors had talked more about uncertainties in their model and conducted laboratory experiments to simulate the effects of global warming on algae, which which would support the results of the algorithm.
“It’s certainly a concern, but there will still be thousands of meteorites per year,” he said via email.
“The main concern is the logistical aspect of searching for Antarctic meteorites, which is already difficult today due to the remoteness of Antarctica. If the results of this study are true, it will force scientists to explore new areas, which may be further from scientific bases than those that are commonly explored. This would make this treasure trove even more inaccessible and, therefore, require more funding and logistical support.”
What we have learned from meteorites in the Antarctic
Meteorites found in the southernmost reaches of the planet teach 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 identified meteorites collected in the region in 1979 and 1981 as coming from the moon, Righter noted. Before these discoveries, there were only samples from the moon 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 are connected to Mars.
“All of this recent research history indicates that, with continued collection, new types of meteorites are likely to be found – including possibly pieces of Mercury or Venus that may have been thrown off their surfaces after an impact.”
Righter, along with the study’s authors, called for the collection efforts to be stepped up and prioritized. “If meteorites are not collected quickly enough, they will be a lost resource for current and future planetary science,” he said.
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