One Big Blast Gave Earth Most of Its Martian Meteorites

A huge meteorite impact on Mars 5 million years ago blasted toward Earth many of the rocks that scientists scrutinize to learn more about the Red Planet, a new study reveals.

The cosmic crash left a 34-mile-wide (55 kilometers) gouge on Mars called Mojave Crater and is the source of all "shergottite" or igneous rock Martian meteorites found on Earth, researchers say. Examining the crater and the meteorites also led to new revelations about how old the rocks are.

Image: Mojave Crater on Mars
A look at Mojave Crater on Mars. The rays are evidence of debris thrown up from an impact that happened about 5 million years ago. The arrow points toward crater clusters used to estimate the age of the region. Science / AAAS

"We tried to find good arguments to convince ourselves that [Mojave Crater] was 5 million years or younger. You don’t expect this size of crater so recently formed, statistically at least," lead author Stephanie Werner, a planetary scientist at the University of Oslo in Norway, told [Mars Meteorites: Red Planet Pieces on Earth (Photos)]

Werner's team first used a technique called crater counting, which estimates a region's age by seeing how many large and small craters are in a particular zone. The more large craters, the older the terrain likely is.

Image: Daytime view of the area surrounding Mojave Crater on Mars
A daytime view of the area surrounding Mojave Crater, shown in a picture taken by Mars Odyssey. Mojave Crater is circled in red. Craters were counted for the plateau units (brown), channel units (blue-grey) and ejecta from Mojave (red line). Science/ AAAS

Through their detective work, Werner said, they found the crater is indeed about 5 million years old. The material blasted from Mojave Crater had fewer meteorite strikes than the surrounding channel floor.

The new study was published Thursday (March 6) in the journal Science.

— Elizabeth Howell,

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