Meteorites that strike Earth don’t always come from the deepest regions of our solar system—sometimes they originate from one of our closest planetary neighbors. In fact, researchers over the years have recovered hundreds of rocks that got their start on Mars. Now, experts believe they have sourced around 200 of those meteorites to five specific impact craters located in two volcanic regions on the Red Planet. With more analysis, researchers believe these samples will help them better understand the geological history of Mars.
Previous attempts to trace Martian meteorite origins have proven largely unsuccessful because they relied on a technique called spectral matching, in which a material’s composition is compared based on the patterns of light they are capable of emitting or absorbing. Trying to do this for a source that is millions of miles away and covered in dust, however, made the results unreliable and difficult to obtain.
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But in a study published on August 16 in the journal Science Advances, a team from the University of Alberta calculated that around half of the 10 known Martian meteorite subgroups here on Earth come from specific areas of Mars. The findings rely on improved Martian physics modeling, which is key to understanding the ejection process resulting from an asteroid impact. Researchers combined this better understanding of ejection dynamics with remote sensing data detailing the geological makeup of Mars to narrow down the meteorites’ origins.
According to Chris Herd, a study co-author, professor of earth and atmospheric sciences, and curator of UA’s Meteorite Collection, this “major advance” unlocked the ability to revise previous, limited calculations.
“I call that the missing link—to be able to say, for example, the conditions under which this meteorite was ejected were met by an impact event that produced craters between 10 and 30 kilometers (roughly 16-38 mi) across,” he said in a university statement on August 19.
While one might think only comparatively gigantic impacts are strong enough to send hunks of a planet beyond its atmosphere, that’s actually not the case. But thanks to 5 km/s (8 mi/s) ejection speeds, even a blast that only results in a 5-mile-wide crater is theoretically powerful enough for rocks to escape Martian gravity, enter into an orbit around the Sun, and eventually find themselves pulled towards Earth. Astronomers believe Mars faced 10 events that flung debris into space in the planet’s recent history.
“Now, we can group these meteorites by their shared history and then their location on the surface prior to coming to Earth,” Herd explained.
Researchers are now confident that five of those craters spread throughout a pair of volcanic regions known as Tharsis and Elysium are likely responsible for the roughly 200 meteorites detailed in the study.
Armed with this new information, researchers can now begin revising Martian chronology in ways that may affect timing, duration, and details of many separate planetary events throughout its existence. Herd said additional analysis may allow them to reconstruct Martian volcanic stratigraphy—the record of a planet seen through its geological layers.
“This will fundamentally change how we study meteorites from Mars,” Herd said.