Mars’ atmosphere was significantly changed by a 500 million-year period of hugely violent eruptions from ancient volcanos
Scientists previously thought that the number of huge depressions in the Martian surface were caused by asteroids, but the impacts were not perfectly round – as would be expected by craters – but instead had deep floors and benches of rock near the walls, signifying collapse.
A region in the north of the Red Planet, called Arabia Terra, was the source of some of the most violent volcanic explosions ever discovered. These eruptions spewed water vapor, carbon dioxide, and sulphur dioxide into the air over a 500 million-year period, approximately four billion years ago.
Researchers found evidence of ash, which is easier to discover than the volcanos themselves, and found numerous minerals associated with altered volcanic activity.
This discovery will help scientists understand how planets and moons are formed, as similar processes are possible in regions of Venus, Jupiter’s moon Io, and in Earth’s own history.
The scientists looked for ash in the walls of canyons and craters thousands of miles from where they believed the volcanos would originally be, due to Martian winds, they discovered volcanic minerals turned to clay by water such as montmorillonite, imogolite, and allophane.
However, some questions remain unanswered: how can Mars have only type of volcano in that region? On Earth, volcanos capable of the kind of super eruptions scientists believe happen on Mars are dispersed around the globe, but its possible that they were once closer and have been eroded physically and chemically.
“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?’” said Jacob Richardson, a geologist at Nasa.
The equivalent of 400 million Olympic-size swimming pools of molten rock and gas would have been blasted from Mars’ core to the surface, after which the volcano collapses causing a caldera – seven of which were discovered in Arabia Terra.
Each of the eruptions would have had huge impacts on Mars’ climate, such as making the atmosphere thicker or blocking the Sun’s rays and making the planet cooler.