NASA confirms thousands of massive and ancient volcanic eruptions on Mars

Some volcanoes can produce eruptions so powerful that they release oceans of dust and toxic gases into the air, blocking sunlight and altering a planet’s climate for decades. By studying the topography and mineral composition of part of the Arabia Terra region in northern Mars, scientists recently found evidence of thousands of such eruptions, or “super eruptions,” which are the most violent volcanic explosions. known.

Spewing water vapor, carbon dioxide, and sulfur dioxide into the air, these explosions tore the Martian surface apart over a period of 500 million years, roughly 4 billion years ago. Scientists reported this estimate in an article published in the journal Geophysical research letters in July 2021.

“Each of these eruptions would have had a significant climate impact – perhaps the gas released made the atmosphere thicker or blocked the Sun and made the atmosphere cooler,” said Patrick Whelley, a geologist at Goddard Space. NASA Flight Center in Greenbelt, Maryland, which led the analysis of Arabia Terra. “Martian climate modellers will have work to do in trying to understand the impact of volcanoes. up to thousands of kilometers from the eruption site, a volcano of this magnitude collapses into a giant hole called a caldera. Calderas, which also exist on Earth, can be tens of kilometers wide. Seven calderas in Arabia Terra were the first telltale signs that the region may have already hosted volcanoes capable of super eruptions.

Once thought to be depressions left by the impacts of asteroids on the Martian surface billions of years ago, scientists first proposed in a 2013 study that these basins were volcanic calderas. They noticed that they weren’t perfectly round like craters and showed signs of collapsing, such as very deep soils and boulders near the walls.

“We read this article and were interested in the follow-up, but instead of looking for the volcanoes themselves, we looked for the ash because you can’t hide this evidence,” Whelley said.

Whelley and her colleagues got the idea to search for evidence of ash after meeting Alexandra Matiella Novak, a volcanologist at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. Matiella Novak was already using data from NASA’s Mars Reconnaissance Orbiter to find ash elsewhere on Mars, so she teamed up with Whelley and her team to specifically research Arabia Terra.

The team’s analysis followed the work of other scientists who had previously suggested that minerals on the surface of Arabia Terra were of volcanic origin. Another research group, learning that the basins of Arabia Terra could be calderas, had calculated where the ash from possible super eruptions in this region would have been deposited: moving downwind to the east, they would dilute far from the center of the volcanoes, or in this case, what remains of them, the calderas.

So we picked it up at that point and said, ‘OK, well, these are minerals that are associated with weathered volcanic ash, which has already been documented, so now we’re going to look at how the minerals are. distributed to see if they follow the pattern we would expect to see super blowouts, ”said Matiella Novak.

The team used images from MRO’s compact reconnaissance imaging spectrometer for Mars to identify minerals on the surface. Looking into the walls of canyons and craters hundreds of thousands of kilometers from the calderas, where the ash was said to have been carried by the wind, they identified volcanic minerals transformed into clay by water, including montmorillonite, the imogolite and allophane. Then, using images from MRO cameras, the team produced three-dimensional topographic maps of Arabia Terra. By overlaying the mineral data on topographic maps of the canyons and craters analyzed, the researchers were able to see in the mineral-rich deposits that the ash layers were very well preserved. the same way it would have been when it was cool.

“That’s when I realized it wasn’t a fluke, it’s a real signal,” said Jacob Richardson, a NASA Goddard geologist who worked with Whelley and Novak. . “We are actually seeing what was predicted and it was the most exciting time for me.”

The same scientists who initially identified calderas in 2013 also calculated how much material would have exploded from volcanoes, based on the volume of each caldera. This information allowed Whelley and his colleagues to calculate the number of eruptions needed to produce the thickness of ash they found. It turned out that there were thousands of eruptions, Whelley said.

One open question is how a planet can have a single type of volcano littering an area. On Earth, volcanoes capable of super eruptions – the most recent erupted 76,000 years ago in Sumatra, Indonesia – are scattered around the world and exist in the same areas as other types of volcanoes. Mars also has many other types of volcanoes, including the largest volcano in the solar system, called Olympus Mons. Olympus Mons is 100 times larger in volume than Earth’s largest volcano, Mauna Loa in Hawaii, and is known as a “shield volcano”, which drains lava along a gently sloping mountain. Arabia Terra has the only evidence of explosive volcanoes on Mars to date.

It is possible that the super-eruptive volcanoes were concentrated in regions of the Earth, but were physically and chemically eroded or moved around the globe as the continents moved due to plate tectonics. These types of explosive volcanoes could also exist in regions of Jupiter’s moon Io or could have been clustered on Venus. Either way, Richardson hopes Arabia Terra teaches scientists something new about the geological processes that help shape planets and moons.

“People are going to read our newspaper and say to themselves, ‘How? How could Mars do this? How can such a small planet melt enough rock to power thousands of super eruptions in one place? “, did he declare. “I hope these questions will prompt much more research.