Though scientists have established that Mars spins a little faster each year, the cause of this remains a mystery. A new study published in the Journal of Geophysical Research: Planets suggests the reason could originate with an underground volcano.

The plume could both explain the planet’s rotation and account for how it retains geological heat longer than expected.

Rare Active Volcano on the Red Planet

“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. “Understanding Mars will help in understanding our solar system, as its history is laid out on the red soil.”

Mars has some of the largest mountains and volcanoes in the solar system because the planet, seemingly, doesn’t have plate tectonics, or the shifting plates that create much of the volcanic activity on Earth. The lava from Mars’ ancient volcanoes piles up and builds bigger structures over time.

This is how the Tharsis volcanic province formed, which is a volcanic region that encompasses 3,700 miles. NASA’s InSight lander has been studying the planet’s interior for years, providing scientists with insights regarding the crust’s thickness.

The data from InSight was used to run computer simulations to test what structures could explain the volcanic region. In the mantle beneath the region, the models showed a plume of abnormally light material called a “negative mass anomaly,” or something less dense than surrounding rock.

Researchers believe the anomaly could explain how this region became so filled with volcanoes and whether volcanic activity could be possible in the future.

“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.

Then, researchers used the simulations to calculate whether the less-dense material beneath the Tharsis region could shift the mass inside Mars enough to account for the increased spin rate of the planet. Root compared this process to a person spinning in a desk chair while holding heavy books. If the books are pulled inward, the person begins to spin faster, and Mars may be doing something similar.

“A negative mass flowing upwards means something heavier needs to go down, and because the mass anomaly is located on the equator of Mars, this means the heavier mass is going closer to [the] rotation axis, hence a speed up,” Root stated.