Mars’ era of Ash Fall

Volcanoes are remarkably common. They act as pressure release valves for rocky worlds, as magma, ice, and other materials escape from the worlds heated interiors like steam from an Instapot. Not all eruptions are the same, however. As we look across our world and others, we are realizing that super eruptions that rewrite entire regions can occur.

On Mars, researchers led by Patrick Whelley have documented a history of explosive eruptions on the Arabia Terra that blanketed the region in layers of ash and aluminium-rich minerals. This ash is 100–1000 m deep and is likely the result of between 1000 and 2000 eruptions that occurred over 500 million years.

Martian Map highlighting the sight of super eruptions. Credit: NASA.

According to Whelley, “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. Modelers of the Martian climate will have some work to do to try to understand the impact of the volcanoes.”

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. Credit: NASA/JPL-Caltech/University of Arizona

Most fascinating to me is the timing of this volcanism. According to their paper, the eruptions took place during the late Noachian and early Hesperian periods. The Noachian period was when Mars was getting bombarded with small bodies…