scientists’ attempt to uncover the deep past of our solar system

A team of Belgian-Dutch scientists has created the first-ever “treasure map” that shows where Antarctic meteorites are likely to be found. Meteorites are chunks of stone-like material that can be found on the Earth’s surface after falling from space.

Unlike terrestrial rocks, meteorites have been spared the weathering and volcanism of our planet and are therefore considered priceless archive early stages of our solar system. While rocks tell us nothing about the first half billion years of our planet’s life 4.55 billion years old, most meteorites in the asteroid belt allow us to go back as far as 4.6 billion years. The vast majority of meteorites recorded in Antarctica come from the asteroid belt, with around 1% coming from the Moon and Mars.

Meteorites in Antarctica

Meteorites fall regularly on the surface of the Earth: in France about 50 meteorites weighing more than 10 g rain every year. However, pinning them down is like looking for a needle in a haystack, and scientists from meteorite recovery campaigns often return empty-handed.

On the other hand, it is surprisingly easy to find meteorites in the distant South Pole. This is due to a principle known as concentration mechanismwhere specific ice flows and weather patterns cause meteorites to cluster in rather small areas known as meteor stranding areas.

Satellite observations of factors such as ice flow velocity or surface temperature help scientists predict which areas of blue ice contain meteorites.
Veronique Tollenaar

When meteorites fall on Antarctica, they usually lodge in the ice sheet and drift to the oceans. This has led some to describe the ice as a “natural conveyor belt” for meteorites. Sometimes mountains – sometimes hidden under the ice sheet – can come in their way and redirect them to the surface of the ice sheet.

Meteorites are still found on the surface of areas where the wind has dusted off the snow, leaving blue-tinted ice exposed. These areas are known as blue ice areas. Although meteorites are still recorded in these areas, not all of them contain them.

Once an area of ​​blue ice rich in meteorites has been identified, it is relatively easy to spot the dark colored stones against the light hues of the ice. The success of meteorite searches in Antarctica is unprecedented: more than 60% of meteorites recovered on Earth are located in the Antarctic ice sheet. And the potential remains largely untapped: to date, only a fraction of all blue ice areas in Antarctica have been checked for meteorites, with varying degrees of success.

Determine where to look

To determine where to look for meteorites, we must first understand what differentiates an area of ​​blue ice rich in meteorites from an area without meteorites. To this end, many data are available: the place and the year of discovery of the meteorites are stored in a weather report database. Scientists can also access field reports detailing some of the successful and unsuccessful meteor missions that have been conducted since the discovery of the concentrating mechanism in 1969.

Until now, deciding where to look has been a task for a small number of experts. This means that there is a huge human factor involved in meteorite recovery missions – and it is not possible to assess the potential of every area on a continent that is around 25 times the size of France. To help plan often expensive and logistically complicated missions, our team has developed a map that shows potential meteorite grounding areas.

A scientist collects a meteorite from an area of ​​blue ice. JARE-54/BELARE Expedition 2012–2013 at Nansen Blue Ice Field.

From the real world to the observed world

Make a meteorite “treasure map”, we had to translate the real world into observable numbers. To this end, we applied a grid of cells measuring 450 by 450 meters over the blue ice areas and their close surroundings.

In cases where meteorites have been found in a grid cell, the grid cell is labeled as “positive”. The remaining grid cells are unlabeled. Each cell contains information from satellite and radar observations, including surface temperature, ice flow velocity, surface cover types, or slope. This data allows us to predict where we can find meteorites.

Machine Learning for Continent-Scale Predictions

A lot of data is fed into the meteor prediction algorithm.
Veronica Tollenaar/ULB

Machine learning and statistical models make it possible to combine these different observations and to take into account any uncertainties linked to the data. The performance of the prediction algorithm is optimized through several iterations. Each time, the algorithm’s predictions are checked against several areas known to harbor meteorites or not.

The work of the algorithm can be divided into several stages. First, the algorithm learns what constitutes a typical positive or unlabeled grid cell. After learning the data for the different grid cells, the algorithm can calculate the probability that an unlabeled grid cell does or does not contain meteorites.

Grid cells that potentially contain meteorites are then grouped into meteor stranding areas, with areas ranging from a few to hundreds of square kilometers. Our research shows that the accuracy of these predicted meteor stranding areas is estimated at more than 80%.

The analysis of the predicted areas confirms that the machine learning algorithm succeeds in capturing the interaction between different phenomena. While opportunities to find meteorites abound across the continent, some areas near existing research stations remain unexplored, making a reconnaissance visit very attractive.

The “treasure map” heralds a new era for meteorite searches in Antarctica. By sharing our research with colleagues around the world, we approach meteorite collecting as a community-wide collaborative effort. In response, scientists from countries as varied as Korea, India, Chile or the United States have shown interest in exploring the areas indicated.

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