Scientists may have discovered the source of recently active volcanism on Mars.
A massive, 4,000-kilometer (roughly 2,500-mile) wide convection plume in the Martian mantle could be driving molten magma up to the surface beneath a broad plain called the Elysium Planitia. This could explain several lines of evidence pointing to a volcanic Mars.
“Our results demonstrate that the interior of Mars is geodynamically active today,” write planetary geophysicists Adrien Broquet and Jeffrey Andrews-Hanna of the University of Arizona, “and imply that volcanism has been driven by mantle plumes from the formation of the Hesperian volcanic provinces and Tharsis is the past to Elysium Planitia today.”
Mars has demonstrated very convincing evidence of being geologically dead, both inside and out. Its relatively old surface, which appears to be devoid of recent volcanic resurfacing and tectonic motion, and the absence of a global magnetic field have been held up as reasons to believe there’s nothing but firm, motionless rock all the way down to the core.
Recent observations have cast serious doubt on the idea of a completely dead Mars. A meteorite from Mars that made its way to Earth, for example, showed signs of mantle convection as recently as half a billion years ago.
Then, in a fissure system known as the Cerberus Fossae, satellite photos revealed evidence of volcanic surface deposits as young as 50,000 years old.
Then, Mars InSight, a lander that has been watching the interior of Mars since November 2018, discovered a significant amount of ongoing seismic activity that is consistent with volcanism.
There have been a few other strange observations. The local gravity field of Elysium Planitia, for example, is unusually strong, indicating subsurface activity.
Broquet and Andres Hanna gathered topographical, gravity, geological, and seismic data and set about developing a model to fit it.
A mantle plume, according to their analysis, checks all the boxes. These are hot interior material upwellings that push against a planet’s core-mantle boundary, forcing magma upwards and forming crustal hotspots and surface volcanism.
To match the observed data – including seismic activity epicenters detected by InSight – the plume would be at least 3,500 kilometers across and 95 to 285 Kelvin warmer than its surroundings. That’s a temperature range of 95 to 285 degrees Celsius, or 171 to 513 degrees Fahrenheit.
This is very similar to the prehistoric volcanic activity responsible for extensive surface sculpting on Earth, such as the Deccan Traps and the North Atlantic Igneous Province.
“Although Mars is smaller than the Earth, the formation of similarly large plume heads is expected given the lower gravity and higher viscosity of the Martian mantle,” the researchers write in their paper.
“The best-fit plume head center, based solely on gravity and topography data, is precisely located at the center of the Cerberus Fossae, where both recent volcanism and most marsquakes have been located.”
According to the researchers, Mars would be the third planet in the Solar System to have mantle plume activity, joining Earth and Venus.
It’s a result that has some interesting implications for Mars. Interior heating could keep lakes beneath the Martian surface from freezing solid, rather than surface volcanoes spewing lava everywhere. This has implications for the search for Martian life, as microbes may be hiding in such lakes, living their quiet lives unnoticed by humans.
“Ongoing plume activity demonstrates that Mars is not only seismically and volcanically active today, but possesses a geodynamically active interior as well,” Broquet and Andrews-Hanna write.
“A plume beneath Elysium Planitia also indicates that the surface volcanic flows and seismic activity are not isolated events, but part of a long-lived, actively sustained, regional system, with implications for the longevity and astrobiological potential of subsurface habitable environments.”
The research has been published in Nature Astronomy.
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