A plume of scorching hot rock as wide as the continental United States is rising near Mars’ core and could help explain recent volcanism and earthquakes seen on the Red Planet, scientists say.
Most volcanism on March occurred during the first 1.5 billion years of its history, leaving behind giant monuments such as Olympus Mons, the highest mountain in the solar system. However, scientists largely believed that Mars had cooled since then, essentially becoming dead over the past 3 billion years or so. But in recent years, scientists have seen hints of geological activity after all, and now scientists have found a mushroom-shaped pillar of hot, floating rock beneath a region called Elysium Planitia that could explain the recent findings.
“Our study demonstrates that Mars is not dead,” lead study author Adrien Broquet, a planetary scientist at the University of Arizona in Tucson, told Space.com.
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The narrative around the recent geology of Mars has started to change with a 2021 study that found evidence that Mars could still be volcanically active, with evidence of eruption over the past 53,000 years or so. Using data from satellites orbiting Mars, this search uncovered a previously unknown smooth, dark surface. volcanic deposit covering an area slightly larger than Washington, D.C. The deposit surrounds one of the fissures that make up the 800-mile-wide (1,300 kilometer) young fissure system known as Cerberus Fossae. This area lies within the relatively featureless plains known as Elysium Planitia, located in the northern lowlands near the Martian equator.
Additionally, NASA InSight Lander detected hundreds of earthquakes on the red planet, with most of the largest of these March quakes coming from Cerberus Fossae. Overall, the probe’s findings suggest that the level of seismic activity on Mars is between that of the moon and of Earth.
In the new research, scientists developed geophysical models based on geological, terrain and gravity data from Elysium Planitia. They found evidence that the entire area rests on a mantle plume – a column of hot rock rising from deep within Mars to burn off overlying material like a blowtorch. Broquet said this mantle plume formed about 930 miles (1,500 km) below the surface, at the interface between Mars’ core and the mantle layer, which itself lies between the core and the Martian crust.
“We see that this giant plume is about the size of the continental United States, about 2,500 miles (4,000 km) – which, for a planet smaller than Earth, is even more enormous,” Broquet said. .
Although this is the first mantle plume scientists have found on Mars, geologists have long known about the existence of mantle plumes on Earth. For example, the Hawaiian island chain formed when the Pacific tectonic plate slowly drifted over a mantle plume.
The material of a mantle plume is buoyant relative to the surrounding rock. “It’s lighter, so it floats and migrates upwards, like what you can observe in a lava lamp, where heated oil rises,” Broquet said.
The researchers suggested that the center of the newly detected Martian mantle plume lies precisely beneath Cerberus Fossae. They estimated the plume to be about 170 to 520 degrees Fahrenheit (95 to 285 degrees Celsius) hotter than its surroundings.
Researchers found that the mantle plume pushed the Martian crust more than a mile (1.6 km), bringing hot magma to the Red Planet’s surface and driving the Mars tremors that InSight detected.
“Not only is there young volcanism in this area, but you can see that this volcanism is part of a recent resurgence of activity,” Broquet said. “Before about 100 million years ago, the last major activity in this region was almost 3 billion years ago. Again, something had to happen to cause this volcanic resurgence, and that something is the plume of the mantle.”
Broquet said he suspected Elysium Planitia was the only region on Mars with an active mantle plume, although a second plume may be hiding beneath Tharsis. Tharsis is a 3,000 mile (4,800 km) wide region near the equator in the western hemisphere of Mars that is home to the largest volcanoes in the solar system and where scientists have detected recent and ongoing volcanic activity, he noted.
However, there may be explanations for volcanic activity at Tharsis other than a mantle plume, he said. For example, the crust there is very thick and therefore may have trapped heat, helping to keep the rock molten. In contrast, “in the region of Elysium Planitia, where we found the plume, the crust is known to be significantly thinner, and so we had to invoke another mechanism – i.e. the plume – to induce volcanism,” he said.
Taken together, these findings suggest that Mars is the third body in the inner solar system, after Earth and Venuswhere mantle plumes are currently active.
“We used to think that InSight had landed in one of the more geologically dull regions of Mars – a nice flat surface that should be roughly representative of the planet’s lowlands,” Broquet said. “Instead, our study demonstrates that InSight landed just above an active plume head.”
The new findings could also have implications for the search for life on Mars, the researchers said. The area where they discovered the plume also has the most recent evidence of liquid water flowing over the Red Planet’s surface. Since there is life virtually anywhere there is water on Earth, scientists often focus the search for extraterrestrial life on sites that have water.
“Water ice is still thought to be present in Mars’ subsurface, and so if the plume is still providing heat, which we think is the case, pockets of liquid water or aquifers could be present alongside magma chambers in the crust of the Elysium Planitia region,” Broquet said. “On Earth, microbes thrive in environments like this. Therefore, I would argue that the plume has implications for the astrobiological potential of Mars today. A next step could be to estimate if these aquifers are present and where they might be.”
It is still unclear how a mantle plume could have formed recently on a cooling Mars.
“A plume typically takes a few hundred million years to rise from the core-mantle boundary to the surface,” Broquet said. “Once it reaches the surface, our experience on Earth tells us that the plume remains active for a few tens to a few hundred million years. So geologically speaking, this plume formed and reached the base of the crust quite recently, that’s what’s surprising. It’s not an old plume that survived the history of Mars.”
Broquet noted that scientists once thought the moon was also geologically dead. “Due to its small size, it was expected to cool faster than Earth,” he said. “However, seismic data recorded during the Apollo era was used to show that the moon’s core is molten, and it was a big surprise. The moon is not cold and dead – it still has some warmth inside.”
Similar to those discoveries on the moon, “our finding is a paradigm shift for our understanding of Mars evolution,” Broquet said. “Such a large mantle plume is not predicted by the current model of the thermal evolution of Mars. Future studies will have to invoke a new mechanism and a new geological history to find a way to account for a very large plume. coat that shouldn’t be there.”
Overall, “there’s a lot of fundamental physics inside a planet that we obviously don’t understand,” Broquet said. “Like when we thought the moon was dead.”
The research is described in a paper (opens in a new tab) published Monday, December 5 in the journal Nature Astronomy.
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