Heat from a volcano erupting beneath a glacier on Mars may have created large lakes in the relatively recent past, according to a new study. Hundreds of cubic kilometers of liquid water may have been present for hundreds, even thousands of years. And as we know by now, where there’s a hint of water, there’s also the possibility of life.
One of the largest mountains in the solar system, the Martian volcano Arsia Mons is nearly twice as high Mount Everest. Scientists have speculated since the 1970s that the northwest flank of the tropical volcano was once covered by glacial ice. Then, about a decade ago, researchers showed how the terrain around the giant volcano shows striking similarities to features left by receding glaciers in the Dray Valleys of Antarctica: piles of rubble deposited at the edges of a flowing glacier.
Using data from NASA’s Mars Reconnaissance Orbiter, a team led by Kathleen Scanlon from Brown University surveyed the glaciovolcanic landforms in the glacial deposits on the volcano, looking for evidence that lava flowed the same time that the ice was present. They found several features indicative of volcano-ice interactions: pillow and hyaloclastite mounds, ice-confined flows, and a tuya.
On Earth, pillow and hyaloclastite formations occur when lava erupts at the bottom of an ocean or a glacier. When the pressure of the ice sheet constrains lava flow, and glacial meltwater chills the lava into volcanic glass bits, mounds and ridges are formed with steep sides and flat tops, called tuyas. The new analysis also turned up evidence of a river that formed in a jökulhlaup (“glacier run”), a giant outburst flood that occurs when water trapped by, or under, a glacier breaks free.
According to the study, heat from the eruptions along the northwest flank -- when a glacier covered the area around 210 million years ago -- would have melted massive amounts of ice, forming “englacial lakes,” like liquid bubbles you’d find in a mostly-frozen ice cube.
Using basic thermodynamics, they calculated that the eruption of hundreds of cubic kilometers of subglacial lava would have produced a similar volume of liquid meltwater. Two of the deposits would have created lakes containing around 40 cubic kilometers of water each, for example, while another of the formations would have created around 20 cubic kilometers.
Additionally, their back-of-the-envelope calculation estimates that these bodies of meltwater may have persisted on 100 to 1,000-year timescales. That may have been long enough for, say, microbes to colonize the lakes.
According to recently developed climate models for Mars, during periods of increased axis tilt, ice now at the poles would have moved toward the equator. That makes giant mid-latitude mountains like Arsia Mons prime locations for glaciation around 210 million years ago. That means that this giant volcano may have been home to one of the most recent habitable environments found on Mars. Other possibilities turned up by various rovers were older than 2.5 billion years. "If signs of past life are ever found at those older sites, then Arsia Mons would be the next place I would want to go," Scanlon says in a news release.
The work was published in Icarus this week.
Image: NASA/Goddard Space Flight Center/Arizona State University/Brown University