Scientists found evidence that a region of northern Mars called Arabia Terra experienced thousands of "super eruptions," the biggest volcanic eruptions known, over a 500-million-year period.
Some volcanoes can produce eruptions so powerful they
release oceans of dust and toxic gases into the air, blocking out sunlight and
changing a planet’s climate for decades. By studying the topography and mineral
composition of a portion of the Arabia Terra region in northern Mars,
scientists recently found evidence for 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 through the Martian surface over a
500-million-year period about 4 billion years ago. Scientists reported this
estimate in a paper published in the journal
Geophysical Research Letters in July 2021.
“Each one of these eruptions would have had a
significant climate impact — maybe the released gas made the atmosphere thicker
or blocked the Sun and made the atmosphere colder,” said Patrick Whelley, a geologist at NASA’s
Goddard Space Flight Center in Greenbelt, Maryland, who led the Arabia Terra
analysis. “Modelers of the Martian climate will have some work to do to try to
understand the impact of the volcanoes.”
NASA Goddard scientist, and Arabia Terra study lead author, Patrick Whelley, preparing for a 3D laser scan survey at the site of the 1875 explosive eruption of the Askja Volcano, Iceland, Aug. 2, 2019. Credits: Jacob Richardson / NASA Goddard
After blasting the equivalent of 400 million Olympic-size swimming pools of
molten rock and gas through the surface and spreading a thick blanket of ash up
to thousands of miles 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 dozens of miles wide. Seven calderas in Arabia Terra were the
first giveaways that the region may once have hosted volcanoes capable of super
eruptions.
Once thought to be depressions left by asteroid impacts to 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 they had some signs of collapse, such as very deep
floors and benches of rock near the walls.
“We read that paper and were interested in following up, but instead of
looking for volcanoes themselves, we looked for the ash, because you can’t hide
that evidence,” Whelley said.
Whelley and his colleagues got the idea to look for evidence of ash after
meeting Alexandra
Matiella Novak, a volcanologist at the Johns Hopkins
Applied Physics Laboratory in Laurel, Maryland. Matiella Novak already had been
using data from NASA’s Mars
Reconnaissance Orbiter to find ash elsewhere on Mars, so
she partnered with Whelley and his team to look specifically in Arabia Terra.
The team’s analysis followed up on the work of other scientists who earlier
suggested that the minerals on the surface of Arabia Terra were volcanic in
origin. Another research group, upon learning that the Arabia Terra basins
could be calderas, had calculated where ash from possible super eruptions in
that region would have settled: traveling downwind, to the East, it would thin
out away from the center of the volcanoes, or in this case, what’s left of
them: the calderas.
“So we picked it up at that point and said, ‘OK, well these are minerals
that are associated with altered 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 from super eruptions,”
Matiella Novak said.
This image shows several craters in Arabia Terra that are filled with layered rock, often exposed in rounded mounds. The bright layers are roughly the same thickness, giving a stair-step appearance. The process that formed these sedimentary rocks is not yet well understood. They could have formed from sand or volcanic ash that was blown into the crater, or in water if the crater hosted a lake. The image was taken by a camera, the High Resolution Imaging Experiment, on NASA's Mars Reconnaissance Orbiter. Credits: NASA/JPL-Caltech/University of Arizona Click here for more information.
The team used images from MRO’s Compact Reconnaissance Imaging Spectrometer
for Mars to identify the minerals in the surface. Looking in the walls of
canyons and craters from hundreds to thousands of miles 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. Then, using images from MRO cameras, the team made three-dimensional
topographic maps of Arabia Terra. By laying the mineral data over the
topographic maps of the canyons and craters analyzed, the researchers 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 Jacob Richardson, a geologist at NASA
Goddard who worked with Whelley and Novak. “We’re actually seeing what was
predicted and that was the most exciting moment for me.”
The same scientists who originally identified the calderas in 2013 also
calculated how much material would have exploded from the 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 there were thousands of eruptions, Whelley said.
One remaining question is how a planet can have only one type of volcano
littering a region. On Earth volcanoes capable of super eruptions — 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 super-eruptive 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, Richardson hopes 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?’” he said. “I hope these questions bring about a lot of other research.
Credits: Madison Dean/NASA Goddard Download video here
For more information about volcanoes in the solar system, check out: How
Earth Volcanoes Offer a Window into the Evolution of Life and the Solar System.
Banner image: Photo of volcanic ash taken in Hawaii on April 8, 2008.
Credits: United States Geological Survey. To download the image, go here.
By Lonnie Shekhtman
NASA's Goddard Space Flight Center, Greenbelt, Md.
Source: NASA
Confirms Thousands of Massive, Ancient Volcanic Eruptions on Mars | NASA
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