Young Mars had its world turned upside-down by some hot stuff. The emergence of a titanic mount of molten rock jostled the Red Planet’s early tropics out of position, and may have helped usher in the cold, dry and dead version of the planet we know today.
That massive bulge of volcanic rock is called the Tharsis region. At 5000 kilometres across and more than 10 kilometres thick, it is the largest known volcanic complex in the solar system. When huge outpourings of lava between 4.1 and 3.7 billion years ago created it, it deformed the entire planet.
It was thought that Tharsis bent the planet’s crust and dictated the direction of Martian rivers, which formed later.
But now, Sylvain Bouley of University of Paris-South and his colleagues suggest that the rivers and their valley networks formed first, and were concentrated along the equator. The formation of Tharsis tilted the planet around so much that, if it happened on Earth, Paris would sit atop the magnetic north pole – a rearrangement that would have wild, catastrophic effects on the climate and water.
“This may make it easier to explain the climate associated with the valley networks,” says Robert Craddock, a geologist at the Smithsonian Institution in Washington DC. “It’s actually pretty obvious, but no one saw it before.”
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