World's First Meteorite 'Treasure Map' Offers Clues to Help Researchers

You wouldn’t know it just by standing outside, but Earth is bombarded daily by 60 tons of debris from asteroids, comets, and other celestial bodies. Nearly all of it burns up in the atmosphere, with a small percentage impacting as micrometeorites (of which you can even find mixed in the collective dust of urban rooftops) and an even smaller amount—about 6,000 annually—large enough to find with the naked eye. 

Now, naturally, besides the good fortune (or sometimes misfortune) of being in the right place at the right time, finding these prized ancient rocks is no easy feat. For one thing, most meteors plunge directly into a body of water. Those that hit land can be difficult to spot among other rocks, with nature quickly erasing tell-tale impact sites. 

Fortunately for researchers who value meteorites for the insights they provide into the origin and evolution of the solar system, there is one place on Earth where extraterrestrial rocks find it difficult to hide: Antarctica. 

“There are probably fewer meteorites falling per acre of land in Antarctica than in other parts of the world,” Ralph Harvey, principal investigator at the National Science Foundation’s Antarctic Search for Meteorites program and a professor at Case Western Reserve University, told NBC News. “But if you want to find things that fell from the sky, lay out a big white sheet. And Antarctica is a 5,000-kilometer-wide [3,100 mi] sheet.”

Finding meteorites in Antarctica is so relatively “easy” compared to the rest of the world that an estimated two-thirds (around 45,000) of those ever discovered have come from the icy continent. The challenge, however, comes not only from the inhospitable conditions and near-inaccessible terrain, but also from knowing where to look to make any expedition worth the cost and danger. Researchers have limited time and resources to strike the extraterrestrial jackpot. 

‘X’ Marks the Spot

In an effort to vastly improve the collection rate of Antarctic meteorites, a Belgian-Dutch team of scientists has unveiled what they’re calling a “treasure map” for the region. 

"Through our analyses, we learned that satellite observations of temperature, ice flow rate, surface cover and geometry are good predictors of the location of meteorite-rich areas," Veronica Tollenaar, who led the study, told Universe Today. "We expect the 'treasure map' to be 80 percent accurate."

How exactly can a map with locations never before visited by researchers promise accuracy as high as 90% in some spots for finding meteorites? Unlike the rest of the world, when a meteorite slams into Antarctica, it’s less a final resting place and more a continuation of a journey. Ice tends to act as a kind of conveyor belt for surface debris and figuring out its ejection points is key to striking the meteorite jackpot. 

After landing in the snow, a meteorite will slowly be incorporated into the ice sheet and carried away. Over time, it will either be discharged into the ocean or brought back to the surface of what’s known as a “blue ice” area. In these special locations on the ice sheet, annual ablation (usually by sublimation) exceeds new accumulations of snowpack. As meteorites emerge, their color contrasts against the deep blue ice, making them easy to spot and retrieve. 

To pinpoint locations of promising meteorite-rich locations (also known as Meteorite Stranding Zones or MSZs), research teams in the past have had to rely on remote sensing data of blue ice areas, followed by costly field reconnaissance visits via helicopter or snowmobile. 

After studying conditions that produce the most meteorite finds, as well as successes and failures of previous blue ice expeditions, Tollenaar and her team decided to leverage machine learning to apply their data to the entire continent. The map it generated contains more than 600 promising new MSZs, many of which remain unexplored. They estimate that these sites collectively may contain anywhere from 340,000 to 900,000 surface meteorites. 

“The disclaimer is this is just based on modeling,” Zekollari told NBC News. “But we hope it can make some missions more successful.”

The researchers add that these locations also likely feature rare meteorites, such as angrites (at 4.55 billion years, the oldest igneous rocks), brachinitres (leftover debris from an ancient planetary body in the asteroid belt that no longer exists), or even Martian meteorites (of which only 126 have ever been found). 

“Collecting this unique and well-preserved material will further enhance the understanding of our Solar System,” they write.