Orbital observations reveal a massive mantle plume pushing up the surface of Mars and leading to intense volcanic and seismic activity

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On Earth, changing tectonic plates modify the surface of the planet and form a dynamic interior, so the absence of such processes on Mars has led many to think of it as a dead planet, as not much has happened in the past three billion years.

In the current issue of natural astronomyScientists from the University of Arizona challenge current views of the geodynamic evolution of Mars by reporting the discovery of an active mantle plume that pushes the surface up and causes earthquakes and volcanic eruptions. The findings suggest that the planet’s deceptively quiet surface may be hiding a much more boisterous interior than previously thought.

“Our study presents multiple lines of evidence revealing the presence of an active giant mantle plume on Mars today,” said Adrien Broquet, a postdoctoral researcher at the UArizona Lunar and Planetary Laboratory and co-author of the study with Jeff Andrews. Hanna, associate professor of planetary sciences at LPL.

Mantle plumes are large masses of warm, silty rock that rise from a planet’s depths and push through the middle layer – the mantle – to reach the base of its crust, causing earthquakes, faults and volcanic eruptions. The Hawaiian Islands chain, for example, formed when the Pacific Plate slowly drifted up the mantle plume.

“We have strong evidence of mantle plume activity on Earth and Venus, but this is unexpected on a world as small and presumably as cold as Mars,” Andrews-Hanna said. “Mars was at its most active 3 to 4 billion years ago, and the prevailing view is that the planet is basically dead today.”

“An enormous amount of volcanic activity early in the planet’s history built the tallest volcanoes in the solar system and covered most of the northern hemisphere in volcanic deposits,” Broquet said. “The little activity that has occurred in recent history is usually attributed to passive processes on a cold planet.”

Researchers were drawn to a surprising amount of activity in a nondescript region of Mars called Elysium Planitia, a plain within Mars’ northern lowlands near the equator. Unlike other volcanic regions on Mars, which haven’t seen much activity for billions of years, Elysium Planitia has had major eruptions over the past 200 million years.

“Previous work by our group found evidence in Elysium Planitia of the most recent known volcanic eruption on Mars,” said Andrews-Hanna. “It generated a small volcanic ash eruption about 53,000 years ago, which was mainly geological yesterday.”

The volcanoes in Elysium Planitia originate from Cerberus Fossae, a collection of small cracks that extend more than 800 miles across the surface of Mars. Recently, NASA’s InSight team found that almost all martian earthquakes or quakes originate from this one region. Although this young volcanic and tectonic activity has been documented, the underlying cause has remained unknown.

On Earth, volcanoes and earthquakes tend to be associated with either mantle plumes or plate tectonics, the global cycle of drifting continents that constantly recycles crust.

“We know Mars does not have plate tectonics, so we examined whether the activity we’re seeing in the Cerberus Fossae region is caused by mantle plume,” Broquet said.

mantle plumes, which can be thought of as analogous to hot wax blobs billowing in lava lamps. giving up their presence on Earth through the classic sequence of events. The warm plume material pushes against the surface, lifting and stretching the crust. The molten rock then erupts from the column in the form of flood basalts creating vast volcanic plains.

When the team studied the features of Elysium Planitia, they found evidence of the same sequence of events on Mars. The surface has been raised by more than a mile, making it one of the highest in the vast northern lowlands of Mars. Analyzes of subtle variations in the gravitational field indicated that this uplift is supported by the planet’s depths, consistent with the presence of a mantle plume.

Further measurements showed that the floor of the impact craters is tilted in the direction of the plume, supporting the idea that something pushed up the surface after the craters formed. Finally, when the researchers applied a tectonic model to the region, they found that the presence of a gigantic plume, 2,500 miles wide, was the only way to explain the extension responsible for the formation of Cerberus Fossae.

“In terms of what you would expect to see with an active mantle plume, Elysium Planitia checks all the right boxes,” Broquet said, adding that the discovery challenges models used by planetary scientists to study the thermal evolution of planets. “This mantle plume affected an area of ​​Mars roughly the size of the continental United States. Future studies will have to find a way to account for the very large mantle plume that was not expected to be there.

“We used to think that InSight landed in one of the most geologically boring regions on Mars — a nice flat surface that must be roughly the lowlands of the planet,” Broquet added. “Instead, our study shows that InSight landed directly on top of an active plume.”

The presence of an active plume will affect interpretations of the seismic data recorded by InSight, which must now take into account the fact that this region is far from normal for Mars.

“The presence of an active mantle plume on Mars today is a paradigm shift in our understanding of the planet’s geological evolution, similar to what happened when analyzes of seismographs recorded during the Apollo era showed that the moon’s core was molten,” Broquet said.

The authors say their findings could also have implications for life on Mars. The studied area experienced floods of liquid water in its recent geological past, although the cause has remained a mystery. The same heat from the plume that fuels the ongoing volcanic and seismic activity can also melt ice to make for floods – and trigger chemical reactions that can sustain life deep underground.

“Microbes on Earth thrive in environments like this, and that could be true on Mars as well,” Andrews Hanna said, adding that the discovery goes beyond explaining enigmatic seismic activity and resurgence of volcanic activity. “Knowing that there is an active giant plume beneath the surface of Mars raises important questions about how the planet has evolved over time.” We are convinced that the future holds more surprises. “

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