Strange meteorites have been traced to their source craters on Mars

Mars rocks that were blasted off the surface of the Red Planet millions of years ago have been traced back to craters where they originated, which could transform our understanding of Mars’s volcanism and evolution

By Leah Crane

16 August 2024

An impact crater on Mars, with darker material exposed beneath the reddish dust

NASA/JPL-Caltech/University of Arizona

Six Martian meteorites have been traced back to the craters they were ejected from on Mars millions of years ago. Finding the original sources of these alien rocks will allow us to place them in context, yielding insights about the history of the Red Planet.

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“Being able to identify the impact launch sites for any Martian meteorites has been a challenging goal for a long time,” says Hap McSween at the University of Tennessee, Knoxville, who wasn’t involved in this work. “There have been numerous published attempts before, but none have been very convincing until now.”

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When a rock smashes into Mars or another planet, it causes a spray of debris, some of which can float away through space and eventually hit Earth as a meteorite. Anthony Lagain at Curtin University in Australia and his colleagues used a sophisticated model that matches what we know about the ages of the millions of Martian craters and of the six meteorites that were chipped off the planet’s surface.

“On Mars, you’ve got about 80,000 craters larger than 3 kilometres, so about 80,000 craters that might be the source of these meteorites,” says Lagain. The researchers’ model narrowed this down to about 20 possible sources. Then, they studied the structure of the rocks to find out how much force they had been suddenly subjected to when they were blasted into space, feeding that into another model of the craters themselves. This led them to the original sources of the meteorites and how deep they were probably buried before the impacts that sent them to Earth.

The meteorites are all igneous rocks, meaning they are pieces of solidified lava. Pete Mouginis-Mark at University of Hawai’i at Mānoa says that while there are some questions about whether the properties of the lava flows in these craters completely match the meteorites, if these craters are truly the sources of the rocks, we can learn a great deal about Martian volcanic activity from them.