Space is a violent, dangerous place.
NASA has officially confirmed that a northern region of Mars once underwent thousands of "super-eruptions" for 500 million years, making these ancient volcanic sites the biggest eruptions known to modern science, according to a recent blog post from the agency.
While these "super-eruptions" ceased roughly 4 billion years ago, the evidence points to Mars as once being unmistakably active.
Super-eruptions on Mars blasted the surface open
Some volcanic eruptions are so unconscionably powerful that they churn entire oceans of dust and toxic gases into the air, effectively blotting out sunlight and altering a planet's climate for decades. And, while examining the mineral composition and topography of a northern region on Mars called Arabia Terra, scientists uncovered evidence of thousands of such catastrophic eruptions, also called "super-eruptions", which are more violent than any planetary eruption known. Carbon dioxide, water vapor, and sulfur dioxide were pumped into the air during these explosions, which continued regularly for 500 million years, ending roughly 4 billion years ago. While the study announcing these findings was first published in the journal Geophysical Research Letters in July of this year, NASA's confirmation serves to solidify our grasp of Mars' ancient past.
"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 Geologist Patrick Whelley of NASA's Goddard Space Flight Center in Greenbelt, Maryland, who also led the examination of the Arabia Terra region, in the agency's post. "Modelers of the Martian climate will have some work to do to try to understand the impact of the volcanoes." It's difficult to overstate how massive these eruptions were. An unthinkable volume of molten rock and gas equivalent to 400 million Olympic-size swimming pools blasted through the Martian surface, and painted the sky with a thick cloud of ash extending thousands of miles from the site of eruption.
And, when the most violent stage was finished, the entire volcanic reaction collapses into a huge hole called a "caldera." We also have these on Earth (in fact, you can go see them in active volcanic regions like Hawaii), and they can grow to dozens of miles wide. On Mars, there are seven calderas in Arabia Terra that hinted at the possibility of a troubled, violent past of explosive super-eruptions. While these were initially considered to be the remains of ancient asteroid impacts on the Red Planet's surface from billions of years ago, scientists later proposed that the basins were really volcanic calderas in a 2013 study. The key lied in the asymmetry of the craters, disrupting the round shape one would expect from cosmic impacts, in addition to evidence of collapse like deep floors and groups of rocks adjacent to the walls.
Mars' 'clustered' super-eruptions aren't found on Earth
"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," said Whelley in the post. Eventually, the research team examined images from the Mars Reconnaissance Orbiter's (MRO's) Compact Reconnaissance Imaging Spectrometer to analyze the mineral composition of Mars' surface. With these, three-dimensional topographic maps of the Arabia Terra region were constructed, superimposing mineral data on the topographic maps of craters and canyons, which revealed the highly-preserved nature of the mineral-rich deposits, suggesting that wind and water didn't jumble the material as it came to rest. "That's when I realized this isn't a fluke, this is a real signal," explained Geologist Jacob Richardson at NASA's Goddard, who collaborated with Whelley and the research team. "We're actually seeing what was predicted and that was the most exciting moment for me."
This does raise another question, according to the researchers. Namely, how can a planet have just a single type of volcano smothering an entire region? Earth has had super-eruptions, the most recent (and not the last) of which exploded 76,000 years ago in Sumatra, Indonesia. But they are dispersed throughout the planet, and are always close to regions where other volcanoes have erupted. It could be that clustered super-eruptions were a thing on Earth, long ago, but have since been physically and chemically eroded, or moved to unseen locations as the continents shifted through the eons. But whether or not Earth has what Mars does, there is no shortage of scientific adventure awaiting the humans who will one day set foot on the ancient, frigid world beyond the moon.