Source: cnBeta
Since the discovery of the Adélie meteorite in 1912, scientists have extracted more than 45,000 meteorites from Antarctica's ice. Each of these "space stones" carries a story about the composition of our solar system and the conditions that existed in the early days of its development.
Scientists recently estimated that as many as 300,000 meteorites and their stories are still on the ice waiting to be discovered. And now they have a map showing where they're looking.
February 2, 2022
Because the polar landscape offers some advantages, scientists have been actively searching for meteorites in Antarctica for decades. The contrast between rock and ice and the lack of many terrestrial rocks make meteorites easier to spot. Dry desert environments also help preserve meteorites, some of which fell to Earth more than 1 million years ago.
Still, finding small rocks scattered across an icy landscape covering 14 million square kilometers is a challenge. To increase the chances of being found, scientists have been focusing on searching for "meteorite strandings" — areas where local geology, ice flow, and climatic conditions cause meteorites to accumulate on the surface. Traditionally, such stranded areas have been discovered by accident – usually near research stations or by scanning maps and satellite images of areas with blue ice. Almost all meteorites are found on blue ice, and because blue ice does not have snow cover, meteorites are exposed on the surface.
Glaciologist Veronica Tollenaar of the Vrije Universiteit Brussel and colleagues have been working to identify more of these meteorite hotspots. They developed a all-Antarctic probability map based on a machine learning algorithm combined with previous meteorite discoveries and extensive satellite observations from NASA, the Canadian Space Agency, the U.S. Geological Survey, and commercial sources. "To find meteorites, we needed a favorable combination of several factors," Tollenaar said.
On the map at the top, a high probability of meteorites appearing along the periphery of the continent and near mountainous areas can be noted. That makes sense, because that's usually where blue ice is found. But the researchers showed that the surface temperature and speed of the ice are also important factors.
Tollenaar said: "If the temperature rises too much or the ice flows too fast, we can't find any meteorites." If the temperature is too high, she explains, the meteorite will sink into the melted ice and then disappear from the surface; if the ice flows too fast, the meteorite will be carried off the ice before there is a chance of mass accumulation.
February 27, 2022
The probability of a meteorite in the lower right quadrant of the map is low. Tollenaar thinks the blue ice in this area — near the coast but at low altitudes — is just too hot. Surface temperature data from the Medium Resolution Imaging Spectrometer (MODIS) on NASA's Terra and Aqua satellites suggest that meteorite hotspots are located in blue-ice regions that remain below -9°C 99% of the time.
Tollenaar said: "It is true that extremely warm days separate the blue ice area rich in meteorites from the area without meteorites. In a very short time, the "warm" temperature causes the ice surface to melt — a condition that is more intense around the meteorite due to the dark color with the heat absorbed by the meteorite — which in turn causes the rock to sink into the ice without being detected.
But as the map shows, there are a lot of blue ice zones, and the temperature and speed of the ice seem to be favorable to stranded meteorites. The researchers developed a "where to go" index, which ranks hotspots based on the potential of fieldwork. The Aran Hills area is close to the top of this list. It's relatively close to McMurdo Station, where more than 1,000 meteorites have been found. Also at the top of the list is an undeveloped area of the Fimbulheimen Mountains, located 120 km from Novok-Lazarev Station. Plenty of blue ice in the area is visible in the detailed image above, which was acquired on February 27, 2022 by The International Land Imager on Landsat 8.
Tollenaar was particularly interested in a hot spot located in the Ellsworth Mountains. "This area is quite far from the area where meteorites have been previously found, which shows that the algorithm allows us to do continent-wide analysis to identify potential areas," she said. ”