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Supervolcanoes once erupted on Mars

Giant eruptions billions of years ago left behind huge craters

GIANT ERUPTION  Billions of years ago, ancient supervolcanoes erupted on Mars, digging huge pits into the planet’s surface. One such crater (center, colored gray to show low elevation) stretches about 70 km in diameter, and reaches 1.8 km deep. Colors of surrounding land represent the range of elevations, from high (red) to low (purple-gray).

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Lava-spewing supervolcanoes ripped through Mars’ dusty red surface billions of years ago, a new analysis suggests.

Scientists have identified Martian volcanoes before, but none as violently explosive as the ones Joseph Michalski of the Planetary Science Institute in Tucson and Jacob Bleacher of the NASA Goddard Space Flight Center in Greenbelt, Md., report in the Oct. 3 Nature. “What we’re looking at is a very different beast,” says Bleacher.

When supervolcanoes erupt, they blow their lids completely, ejecting massive amounts of molten rock. Instead of leaving behind mountains of rubble, supervolcano explosions gouge giant craters into a planet’s surface. Because asteroid craters also pockmark Mars, scientists had assumed most of the pits were caused by impacts.

But some craters looked suspicious: They lacked typical impact signatures and were surrounded by ridges of ancient lava flows. Michalski and Bleacher pieced together topographic and other data from Mars-orbiting spacecraft to sketch a picture of the planet’s past surface. Their work is the first to find Martian supervolcanoes.

Because volcanoes belch gas and particles, the findings could help researchers better understand the history of Mars’ atmosphere, a step toward figuring out whether the planet was ever habitable.

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