Northwest Africa (NWA) 7635 — a Martian meteorite found in Algeria in 2012 — has given planetary researchers information about volcanic activity on the Red Planet, and it’s not like anything we’ve ever seen on Earth.
Analysis of NWA 7635 has helped determine that sometime in its 4.5 billion-year history, Mars had a single volcano that erupted continuously for more than 2 billion years. The research appears in the journal Science Advances.
“Our findings offer new clues to how Mars evolved and insight into the history of volcanic activity on the planet,” said study lead author Prof. Tom Lapen, from the University of Houston.
Much of what we know about the composition of rocks from volcanoes on Mars comes from meteorites found on Earth.
Analysis of different substances provides information about the age of the meteorite, its magma source, length of time in space and how long the meteorite was on Earth’s surface.
Something slammed into the surface of Mars more than one million years ago, hitting a volcano or lava plain.
This impact ejected rocks into space. Fragments of these rocks crossed Earth’s orbit and fell as meteorites.
NWA 7635 was found to be a type of volcanic rock called a shergottite.
Eleven of these Martian meteorites, with similar chemical composition and ejection time, have been found.
“Cosmogenic nuclide data demonstrate that NWA 7635 was ejected from Mars 1.1 million years ago, as were at least 10 other depleted shergottites,” the researchers said.
Although the other 10 meteorites in the group were between 327 and 600 million years old, meaning they were formed from cooling magma nearly half a billion years ago on the surface of Mars, NWA 7635 was found to be 2.4 billion years old.
“What this means is that for 2 billion years there’s been sort of a steady plume of magma in one location on the surface of Mars,” said co-author Prof. Marc Caffee, of Purdue University.
“We don’t have anything like that on Earth, where something is that stable for 2 billion years at a specific location.”
Mars is known for the most magnificent volcanoes in the Solar System.
The largest Martian volcano, Olympus Mons, is nearly 17 miles high. That’s almost triple the height of Earth’s tallest volcano, Mauna Kea, at 6.25 miles.
“We don’t know at this point where this particular meteorite came from, whether it was Olympus Mons or some other location,” Prof. Caffee said.
Martian volcanoes can grow to such enormous proportions because, unlike Earth, Mars doesn’t have plate tectonics that constantly shuffle the surface.
So a volcano, like the one that birthed NWA 7635, can plume for billions of years.
“These meteorites are allowing us to conduct geologic science on the surface of Mars, and we haven’t even been there yet,” Prof. Caffee said.
Thomas J. Lapen et al. 2017. Two billion years of magmatism recorded from a single Mars meteorite ejection site. Science Advances 3 (2): e1600922; doi: 10.1126/sciadv.1600922