Volcanic mountains

Early Mars saw volcanic supereruptions, researchers say

Using high resolution images of NASA’s Mars Reconnaissance Orbiterplanetary scientists have discovered 4 billion year old layered deposits containing minerals consistent with weathered volcanic ash in a northern region of Mars called Arabia Earth. They estimate that the volcanic ash observed in this region is the result of between 1,000 and 2,000 individual explosive eruptions over 500 million years.

This image, acquired by NASA’s Mars Reconnaissance Orbiter on October 1, 2020, shows several Arabia Terra craters filled with layered rock. Image credit: NASA/Molly Wasser.

“Several large and deep craters in western Arabia Terra, Mars are considered explosive calderas, a type of volcano capable of producing supereruptions,” said Dr. Patrick Whelley of NASA’s Goddard Space Flight Center and colleagues. colleagues.

“If these craters are calderas, vast layers of volcanic ash should be common in Arabia Terra.”

“While stratified deposits have been observed in Arabia before, so far no deposits have been associated with the suggested calderas.”

In the new research, Dr Whelley and his colleagues used images from the MRO’s Compact Reconnaissance Imaging Spectrometer for Mars to identify minerals from Arabia Terra.

Looking into the walls of canyons and craters hundreds or thousands of miles from the calderas, where the ash would have been carried by the wind, they identified volcanic minerals transformed into clay by the water, including montmorillonite, l imogolite and allophane.

They then produced three-dimensional topographic maps of the Arabia Terra region.

By laying out the mineral data on the topographic maps of the canyons and craters analyzed, they were able to see in the mineral-rich deposits that the ash layers were very well preserved – instead of being mixed by winds and water, the ashes were layered in the same way as it would have been when it was fresh.

“That’s when I realized it wasn’t a fluke, it was a real signal,” said Dr Jacob Richardson, also of NASA’s Goddard Space Flight Center.

“We actually see what was predicted and that was the most exciting moment for me.”

Using data from an earlier study, the researchers calculated the number of eruptions needed to produce the thickness of ash they found.

“It turned out there were thousands of eruptions,” Dr Whelley said.

A remaining question is how a planet can only have one type of volcano littering a region.

On Earth, volcanoes capable of supereruptions – 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 down a gently sloping mountain.

Arabia Terra has so far the only evidence of explosive volcanoes on Mars.

It is possible that super-eruption 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, the authors hope Arabia Terra will teach scientists something new about the geological processes that help shape the planets and moons.

“People will read our newspaper and say, ‘How? How could Mars have done this? How can such a small planet melt enough rock to power thousands of super eruptions in one place? “I hope these questions will lead to a lot of further research,” Dr. Richardson said.

A paper on the results have been published in the journal Geophysical Research Letters.

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Patrick Whelley et al. Stratigraphic evidence of early Martian explosive volcanism in Arabia Terra. Geophysical Research Letters, posted July 16, 2021; doi: 10.1029/2021GL094109