Using high-resolution images from NASA’s Mars Reconnaissance Orbiter, planetary scientists have discovered 4-billion-year-old layered deposits containing minerals consistent with altered volcanic ash throughout a region of northern Mars called Arabia Terra. 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 craters in Arabia Terra filled with layered rock. Image credit: NASA / Molly Wasser.
“Several large and deep craters in western Arabia Terra, Mars are thought to be explosive calderas, a type of volcano capable of producing supereruptions,” said Dr. Patrick Whelley of NASA’s Goddard Space Flight Center and colleagues.
“If these craters are calderas, vast layers of volcanic ash should be common in Arabia Terra.”
“While layered deposits have been observed previously in Arabia, until now, no deposits have been associated with the suggested calderas.”
In the new research, Dr. Whelley and colleagues used images from MRO’s Compact Reconnaissance Imaging Spectrometer for Mars to identify the minerals in Arabia Terra.
Looking in the walls of canyons and craters from hundreds to thousands of km from the calderas, where the ash would have been carried by wind, they identified volcanic minerals turned to clay by water, including montmorillonite, imogolite, and allophane.
They then made three-dimensional topographic maps of the Arabia Terra region.
By laying the mineral data over the topographic maps of the canyons and craters analyzed, they could see in the mineral-rich deposits that the layers of ash were very well preserved — instead of getting jumbled by winds and water, the ash was layered in the same way it would have been when it was fresh.
“That’s when I realized this isn’t a fluke, this is a real signal,” said Dr. Jacob Richardson, also from NASA’s Goddard Space Flight Center.
“We’re actually seeing 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.
One remaining question is how a planet can have only 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 dispersed around the globe and exist in the same areas as other volcano types.
Mars, too, has many other types of volcanoes, including the biggest volcano in the solar system called Olympus Mons.
Olympus Mons is 100 times larger by volume than Earth’s largest volcano of Mauna Loa in Hawaii, and is known as a shield volcano, which drains lava down a gently sloping mountain.
Arabia Terra so far has the only evidence of explosive volcanoes on Mars.
It’s possible that supereruptive volcanoes were concentrated in regions on Earth but have been eroded physically and chemically or moved around the globe as continents shifted due to plate tectonics.
These types of explosive volcanoes also could exist in regions of Jupiter’s moon Io or could have been clustered on Venus.
Whatever the case may be, the authors hope Arabia Terra will teach scientists something new about geological processes that help shape planets and moons.
“People are going to read our paper and go, ‘How? How could Mars do that? How can such a tiny planet melt enough rock to power thousands of super eruptions in one location?’ I hope these questions bring about a lot of other research,” Dr. Richardson said.
A paper on the findings were published in the journal Geophysical Research Letters.
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Patrick Whelley et al. Stratigraphic Evidence for Early Martian Explosive Volcanism in Arabia Terra. Geophysical Research Letters, published online July 16, 2021; doi: 10.1029/2021GL094109
