Martian volcano may have once harboured habitable environment

Researchers have said that the slopes of a giant Martian volcano, once covered in glacial ice, may have been home to one of the most recent habitable environments yet found on the Red Planet

Nearly twice as tall as Mount Everest, Arsia Mons is the third tallest volcano on Mars and one of the largest mountains in the solar system.

According to new research led by Brown University geologists, the analysis of the landforms surrounding Arsia Mons shows that eruptions along the volcano's northwest flank happened at the same time that a glacier covered the region around 210 million years ago.

The heat from those eruptions would have melted massive amounts of ice to form englacial lakes - bodies of water that form within glaciers like liquid bubbles in a half-frozen ice cube.

Working with Brown geologist Jim Head, Boston University's David Marchant, and Lionel Wilson from the Lancaster Environmental Centre in the U.K., Scanlon looked for evidence that hot volcanic lava may have flowed in the region the same time that the glacier was present.

Using data from NASA's Mars Reconnaissance Orbiter, Scanlon found pillow lava formations, similar to those that form on Earth when lava erupts at the bottom of an ocean. She also found the kinds of ridges and mounds that form on Earth when a lava flow is constrained by glacial ice. The pressure of the ice sheet constrains the lava flow, and glacial meltwater chills the erupting lava into fragments of volcanic glass, forming mounds and ridges with steep sides and flat tops. The analysis also turned up evidence of a river formed in a jokulhlaup, a massive flood that occurs when water trapped in a glacier breaks free.

Based on the sizes of the formations, Scanlon could estimate how much lava would have interacted with the glacier. Using basic thermodynamics, she could then calculate how much meltwater that lava would produce. She found that two of the deposits would have created lakes containing around 40 cubic kilometers of water each. That's almost a third of the volume of Lake Tahoe in each lake. Another of the formations would have created around 20 cubic kilometers of water.

Even in the frigid conditions of Mars, that much ice-covered water would have remained liquid for a substantial period of time. Scanlon's back-of-the-envelope calculation suggests the lakes could have persisted or hundreds or even a few thousand years.

The paper has been published in the journal Icarus.