For hundreds of millions of years, lava bubbled up from the depths of Mars, forming a staggering volcano system called the Tharsis Bulge. Its four major volcanoes near the equator — including Olympus Mons, the solar system’s largest — are all taller than Mount Everest. And now, new research reveals that the bulge’s massive size had serious consequences for the Red Planet.
According to a French-led team, the bulge made Mars tip over some 3 billion years ago. Its outer layers, the crust and mantle, rotated until the enormous volcanoes traveled about 20 degrees, from the polar regions down toward the equator.
The research, published in Nature, rewrites the first billion years of Martian history. The team’s climate modeling contradicts existing theory by showing that the river valleys seen on Mars could’ve flowed while Tharsis was still forming, instead of emerging afterward. And the eruption of water-rich gases would’ve helped fuel Mars’ early atmosphere for a while, driving precipitation on a wet planet. But by the time the Tharsis volcanoes let out their final breath, the heat was gone, and the planet was abandoned to an endless, dry winter — a world not too different from what we see today.