Mars used to be a very geologically active world – Valles Marineris is the largest canyon in the Solar System and Olympus Mons is the tallest volcano, over three times as tall as Everest – though most of its activity has waned to just marsquakes, leaving a much more inactive world. But it appears that the interior of the Red Planet is not dead yet. At least according to the latest research.
Researchers have looked at Elysium Planitia a lot when it comes to Mars's geological activity. Most of the marsquakes detected by NASA’s InSight were coming from a region on this vast plain called Cerberus Fossae, the location of the most recent volcanic event on Mars, some 53,000 years ago. Several scenarios have been put forward to explain InSight's detections, mostly involving a passive mechanism like the melting of a thickened crust due to mantle convection or maybe an eruption due to the extension of the lithosphere.
But the authors of this new work, A. Broquet and J. C. Andrews-Hanna, don’t find those explanations satisfactory to explain the detections. Their hypothesis sees that the whole plain lies on top of a vast mantle plume head, 4,000 kilometers (2,500 miles) across.
“Given the ongoing seismicity and recent volcano-tectonic activity, we consider whether Elysium Planitia could be the site of a present-day active mantle plume," the researchers, from the University of Arizona, wrote in the paper. "Mantle plumes are ascending bodies of anomalously hot material originating from the deep mantle or core–mantle boundary that are largely independent of the general convective circulation."
The team looked at the physical features of the areas, as well as the gravity measurements and geological structures, and combined them with models to explain the observed tremors and features. They came to the conclusion that a mantle plume is the best explanation behind the marsquakes detected by InSight as well as the slow opening of the crust beneath Cerberus Fossae. According to their work, the top of the mantle plume is between 95 and 285°C (171 and 51 °F) warmer than the crust above it, which is estimated to be about 10 kilometers (6 miles) thick in that location.
If this finding is indeed confirmed, it would make Mars only the third body in the Solar System where an active mantle exists, joining a very exclusive club that currently contains just Earth and Venus.
The results are published in Nature Astronomy.