A rare active volcano on Mars may be causing the whole planet to spin faster

Scientists know that Mars spins a little faster each year, but the cause has been a mystery. Now, a new study published Feb. 18 in the Journal of Geophysical Research: Planets suggests the reason may lie deep underground, where a huge plume of buoyant rock could be stirring beneath the Red Planet’s crust.

This strange plume could help to explain not just Mars’ quicker rotation but also how the planet holds on to geologic heat far longer than expected — forcing scientists to rethink how small, rocky worlds cool and die.

“The Martian surface is so old and shows all these complex but largely not well understood process[es], which I think we can start to unravel by combining interior with surface,” Bart Root, an assistant professor of planetary exploration at the Delft University of Technology in the Netherlands and first author of the study, told Live Science in an email. “Understanding Mars will help in understanding our solar system, as its history is laid out on the red soil.”

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Mars has some of the largest volcanoes and mountains in the solar system. This is because, unlike Earth, Mars does not seem to have plate tectonics, the shifting crustal plates that drive much of our planet’s volcanic activity. Instead, the lava from Mars’ ancient active volcanoes just sits there, piling up and building far bigger structures over time. This resulted in the formation of the Tharsis volcanic province, a volcano-strewn region that stretches 3,700 miles (6,000 kilometers) across the planet’s surface.

In 2018, NASA sent the InSight lander to the Red Planet to better understand the planet’s interior, which, in turn, could help reveal more about its volcanoes. For years, the lander studied Mars’ interior, giving scientists a direct estimate of the crust’s thickness.

Using data from InSight, Root and the team ran computer simulations to test what kinds of structures could explain why the volcanic region has dominated one side of Mars. Those models pointed to a plume of unusually light material — called a “negative mass anomaly,” or something less dense than the rock that surrounds it — in the mantle beneath the Tharsis region.

According to the researchers, this anomaly may explain how the Tharsis region became so large and full of volcanoes.

“The negative or light mass anomaly will move upwards and hit the lithosphere of Mars, introducing melt pockets that have the potential to penetrate the crust and erupt as volcanoes,” Root said. (The lithosphere is a single rigid outer shell approximately 310 miles (500 km) thick.

This digital-image mosaic of Mars' Tharsis plateau shows the extinct volcano Arsia Mons. It was assembled from images that the Viking 1 Orbiter took during its 1976 to 1980 working life at Mars.

This digital-image mosaic of Mars’ Tharsis plateau shows the extinct volcano Arsia Mons. It was assembled from images that the Viking 1 Orbiter took during its 1976 to 1980 working life at Mars. (Image credit: NASA/JPL/USGS)

The researchers then asked whether that same hidden plume of material could also explain Mars’ strange spin rate. Earlier measurements comparing data from the Viking landers, which explored Mars in the 1970s, with data from InSight showed that Mars’ day is shrinking by roughly 70 microseconds per year. That means the planet is rotating slightly faster over time.

Root and his team used their simulations to calculate whether this less-dense material underneath Tharsis could shift mass inside Mars enough to influence the planet’s spin.

A rare active volcano on Mars may be causing the whole planet to spin faster

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