Mars was volcanically active more than two billion years ago
Ancient meteorites suggest the red planet may have been home to some of the longest-lived volcanoes in the solar system. Evelyn Fetterplace reports.
Mars’ volcanic history stretches back more than two billion years – nearly half the planet’s history – according to an analysis of a piece of a Martian meteorite.
Writing in Science Advances, a team from the US and Denmark led by the University of Houston’s Tom Lapen examined two grams of material from a piece of ancient meteorite. They discovered it was made of volcanic rock which formed 2.4 billion years ago, suggesting some of the longest-lived volcanoes in the solar system may have been on Mars.
Much of what we know about Mars’ geological history comes from meteorites. As of 2014, 132 meteorites – out of more than 61,000 found on Earth – were identified as Martian in origin. We suspect they’re from Mars because they share similar chemistry to rocks analysed by NASA’s rovers trundling over the red planet.
Around a million years ago, something smashed into a Martian volcano or lava plain, blasting rocks into space. Some of these rocks fell to Earth and, in 2012, were was picked up in Algeria.
Lapen and his crew took a scrap of rock from inside one of these meteorites – called Northwest Africa (NWA) 7635 – and analysed its chemical composition using a technique called mass spectroscopy.
NWA 7635’s elemental composition placed it in a class of meteorite called shergottites – rocks formed from molten rock. So they can be used as evidence of volcanic activity at their time of formation.
Another 10 shergottite Martian meteorites, which have similar chemical composition and were ejected around the same time as NWA 7635, have also been found.
"We see that they came from a similar volcanic source," Lapen says.
"Given that they also have the same ejection time, we can conclude that these come from the same location on Mars."
The rocks, the researchers found, formed around 2.4 billion years ago as magma bubbled from a volcanic region and cooled on or near the Martian surface.
And while the meteorite provides information about just one part of Mars, they significantly extend our knowledge of the red planet’s volcanic history. Other shergottite meteorites from Mars have been relatively young: between 327 million and 600 million years old.