Massive lava flow released 3.5 billion years ago tilted Mars

A group of scientists discovered Mars' north and south pole were displaced after a huge volcano spewed massive amount of lava 3.5 billion years ago. The weight of the lava had caused the planet's outer layers to become displaced. The study explained the unexpected location of dry river beds and underground reservoirs of water ice among the other so-far unresolved mysteries of the Red Planet.

The lava flow produced the Tharsis dome plateau, over 5000 square km (2 000 square miles) wide and 12 km (7.5 miles) thick, and Mars' surface was tilted between 20 and 25°. According to the scientists, the Tharsis dome is enormous, especially when compared to the size of Mars. The outcropping of billion tonnes caused the planet's crust and the mantle to swivel around.

"If a similar shift happened on Earth, Paris would be in the Polar Circle. We'd see Northern Lights in France, and wine grapes would be grown in Sudan," said Sylvain Bouley, a geomorphologist at Universite Paris-Sud.

The topography of Mars. Credit: Setterfield

The research has shed new light on many unexplained features on the surface of the Red Planet: "Scientists couldn't figure out why the rivers were where they are. The positioning seemed arbitrary. But when you take into account the shift in the surface, they all line up on the same tropical band," Bouley explained.

The large amounts of frozen underground water should, according to the scientists, be located closer to the pole, and now, taking into the account the newest study, it looks it was there before the shift occurred. New results also explain why the Tharsis dome is located on the "new" equator, exactly where it would need to be for the planet to restore its equilibrium.

The standard chronology, assuming the rivers were formed after the Tharsis dome is now also under question. Even, it the giant lava flows didn't happen, the majority of these waterways would have flowed from Mars' cratered highlands of the southern hemisphere to the low plains in the north.

However, despite the promising outbreak, many questions, such as did the tilt cause the shutdown of planet's magnetic fields, did it contribute to the disappearance of Mars' atmosphere, or cause the rivers to stop flowing, are still unanswered and require further investigation.

Reference:

• "Late Tharsis formation and implications for early Mars" – Sylvain Bouley, David Baratoux, Isamu Matsuyama, Francois Forget, Antoine Séjourné, Martin Turbet & Francois Costard – Nature (2016) – doi:10.1038/nature17171 

Featured image: Olympus Mons – the largest volcano in the Solar System. Image copyright: Kees Veenenbos