The interior of ‘Mars’ is not behaving’, reveals an active mantle plume
For decades, astronomers assumed that Mars was geodynamically dead, a planet without thunderous earthquakes or erupting volcanoes. Although remnants of mighty volcanoes exist on the surface of the Red Planet today, these colossal structures have been dormant for millions of years. With little to no heat turning on the planet’s engine, the scientists reasoned, Mars it was inactive a long time ago.
However, in the last five years, this assumption has been shown to be incorrect. NASA’s InSight mission has detected earthquakes and even evidence of recent volcanism around a region of Mars, known as Elysium Planitia. And now, they think they know why this activity occurs.
In an article published in the magazine nature astronomy (opens in a new tab) On December 5, scientists describe what appears to be the first active mantle plume discovered on the Martian surface. study co-author jeff andrews hanna (opens in a new tab)a planetary geologist at the University of Arizona, called the find a “big surprise.”
The finding suggests that Mars may be cooling significantly more slowly than scientists had anticipated. If this is the case, it could have profound implications not only for the planet’s geology but also for the search for water, or perhaps even extraterrestrial life.
In terms of geology, Mars and Land they have several key differences. The crust of our planet is divided into many tectonic plates, which move and collide with each other, driving geological activity. “On Earth, most volcanism takes place around the boundaries of these plates.” Paul Byrne (opens in a new tab)a planetary geologist at Washington University in St. Louis who was not involved in the new research, told Live Science in an email.
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But Mars lacks separate tectonic plates; instead, its bark is a single continuous sheet that sits on top of the mantle. For this reason, scientists believe that volcanic activity on Mars, both ancient and more recent (geologically speaking), must be the result of mantle plumes.
A mantle plume is an outcropping of hot rocky material from a planet’s mantle, the layer that lies just below the crust like the white of an egg under a shell. Unlike egg white, however, the coat is not liquid. “All of that stuff is really solid,” Andrews-Hanna told Live Science, but “on geologic time scales, it can flow.” This gradual movement of the mantle allows the plumes to bubble to the surface like wax in a lava lamp. In general, plume activity is believed to drive terrestrial activity. volcanoes in places like Hawaii and Iceland.
Researchers have known for some time that volcanoes used to exist on Mars; the largest known volcano in the Solar system, Olympus Mons, was discovered on the Martian surface in 1971. Olympus Mons has been dormant for about 25 million years. Based on what we know of Martian geology, it makes sense that the massive volcano would be quiet.
Smaller celestial bodies tend to cool faster than their larger counterparts. Planets with a thinner mantle, the geologic layer that drives most volcanic activity, are also cooling at an even faster rate. “So in this case at least, size matters,” Byrne said. Mars is about 53% the size of our planet, and its mantle is only 15% as thick. Because of this, scientists have long speculated that Mars should be relatively dead from a volcanic and geological perspective.
This assumption has been challenged in recent years by NASA’s InSight mission, which landed a seismometer on Mars in 2018. Since landing in the Elysium Planitia region, the second-largest volcanic region on Mars, this device has detected a source of seismic activity. “Perhaps 90% of the Marsquakes that we recorded and analyzed come from this region,” says the study’s first author. Adrien Mouthpiece (opens in a new tab)a planetary geophysicist at the University of Arizona, told Live Science.
In 2020, scientists also described fissures in the area that may have been volcanically active as recently as 50,000 years ago. And it turns out that this hot spot is the same place where Broquet and Andrews-Hanna postulate that the mantle plume is bubbling slowly.
They suspect that a mantle plume could explain this unexpected seismic and volcanic activity. “What this tells us is that the interior of Mars is not behaving,” said Andrews-Hanna.
However, a mantle plume and several hundred Marsquakes don’t mean Mars is gearing up for a massive eruption any time soon. Assuming the site is volcanically active, Byrne said, “the amount of energy there is still a small amount of what the planet once had.” In other words, Mars is still cooling, just more gradually than scientists had assumed.
But there is another exciting implication of discovering an active mantle plume on Mars. “The heat coming from the plume could allow there to be water,” by melting the ice that exists under the surface of the planet and the creation of aquifers, Broquet said. If this is the case, Elysium Planitia might be the best place on Mars to search for evidence of past or present life.