Just five impacts on Mars sent hundreds of meteorites to Earth

Meteorites that strike Earth don’t always come from the deepest regions of our solar system; sometimes they come from one of our closest planetary neighbors. In fact, over the years, researchers have recovered hundreds of rocks that originated on Mars. Now experts believe they have found about 200 of those meteorites in five specific impact craters in two volcanic areas on the Red Planet. With more analysis, researchers believe these samples will help them better understand Mars’ geological history.

Previous attempts to trace the origins of meteorites on Mars have largely failed because they relied on a technique called spectral matching, which compares the composition of a material based on the light patterns they can emit or absorb. However, when I tried to do this for a source that was millions of miles away and covered in dust, the results became unreliable and difficult to obtain.

[Related: Watch a meteor’s incredible light show above Spain and Portugal.]

But in a study published Aug. 16 in the journal Scientific progressa team from the University of Alberta has calculated that about half of the ten known subsets of Martian meteorites here on Earth come from specific areas of Mars. The findings are based on improved physics models of Mars, which are 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 composition of Mars to narrow down the origins of the meteorites.

According to study co-author Chris Herd, professor of earth and atmospheric sciences and curator of UA’s Meteorite Collection, this “major advance” has opened up the possibility of revising previous, limited calculations.

“I call that the missing link – to be able to say, for example, that the conditions under which this meteorite was ejected were caused by an impact that created craters between 10 and 30 kilometers in diameter,” he says. said in one statement from the university on August 19.

While you might think that only relatively gigantic impacts would be strong enough to send parts of a planet beyond its atmosphere, that’s actually not the case. But thanks to ejection speeds of 5 km/s, even an explosion that only results in a 5-mile-wide crater is theoretically powerful enough to send rocks escaping Mars’ gravity and into orbit around the sun. eventually they are drawn to Earth. Astronomers believe that Mars has experienced 10 events in the planet’s recent history that ejected debris into space.

“Now we can group these meteorites by their shared history and then by their location on the surface before they came to Earth,” Herd explains.

Researchers now believe that five of those craters, spread across a pair of volcanic regions known as Tharsis and Elysium, are likely responsible for the approximately 200 meteorites described in the study.

Armed with this new information, researchers can now begin to revise Mars’ chronology in ways that could affect the timing, duration and details of many individual planetary events throughout its existence. Herd said additional analysis could allow them to reconstruct Mars’ volcanic stratigraphy — the record of a planet seen through its geological layers.

“This will fundamentally change the way we study Martian meteorites,” Herd said.