Enormous Mantle Plume Reveals Mars Is Still Geologically Active

Mars has a reputation as a cold, dead world, but a new study suggests that may be only partially accurate. Researchers from the University of Arizona have analyzed a region that appears to be geologically boring by Martian standards, finding evidence the mantle is pushing upward, causing fissures, swelling, and quakes. This potential mantle plume could mean Mars is much more geologically active than it first appears.

We know that Mars was extremely geologically active in the past, as evidenced by the presence of the tallest volcanoes in the solar system. The planet cooled dramatically between three and four billion years ago, but perhaps it didn’t cool as much as believed. The region in question is known as Elysium Planitia, a flat area of the planet’s northern lowlands. That may sound familiar because that’s where NASA’s InSight lander set up shop several years ago to study the planet’s internal structure. And wouldn’t you know it, the probe’s analysis of “marsquakes” shows that almost all of them originate around a series of fissures in Elysium Planitia known as Cerberus Fossae.

The researchers were initially drawn to the region because it shows evidence of more recent geological activity within the last 200,000 years, including an eruption a mere 58,000 years ago. The evidence shows that Elysium Planitia has been uplifted by more than a mile, indicating there is a mantle plume below the surface. A plume is simply a large blob of molten rock that rises from the mantle to the crust, where it can cause faults, quakes, and volcanic activity. The team even found that crater floors in Elysium Planitia are tilted toward the plume, which shows the swelling occurred after those craters were formed.

Cerberus Fossae as seen by the European Space Agency’s Mars Express orbiter.

When applying a tectonic model to the data, the team found a mantle plume was the only plausible explanation. Measurements show the plume measures about 2,500 miles across, which would be large even for Earth. It all adds up to a planet that has more going on under the surface than anyone thought. Future studies will have to explore the origins of this apparent mantle plume in a region where no one expected to find one.

While InSight provided invaluable data on the planet’s seismic events, the mission didn’t go exactly to plan. The lander carried a burrowing heat probe that was supposed to take the planet’s temperature, and surely that data would have been of great value in understanding the mantle plume hypothesis. However, the probe was never able to make any progress in the smooth Martian soil. NASA called off the experiment in early 2021. InSight itself is expected to go offline in the coming weeks as it struggles to collect power with its dusty solar panels.

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