Aram Chaos: a lake in warmer times (ESA/DLR/FU Berlin/G. Neukum)

Noah would have loved this. Mars probably had its own colossal flood millions of years ago, when an ice-covered lake cracked open and gushed to the surface. The scenario hints that buried lakes sheltered microbes that may even now lie dormant in subsurface ice.

On Mars, several huge channels seem to originate in the boulder-strewn floors of deep chasms and impact craters.

“Huge amounts of water had to flow through these channels,” says Victor Baker at the University of Arizona in Tucson. But the terrain dates from a time when Mars was evolving into the cold desert we see today. Where did the water come from?

Manuel Roda at Utrecht University in the Netherlands took a closer look at a crater called Aram Chaos. It has a channel 10 kilometres wide and 2 kilometres deep leading away from it. To carve such a channel, Roda and his team calculate that almost 90,000 cubic kilometres of water must have flowed through it for perhaps a month.


Wake up, Martians

The team thinks that a lake filled the crater when Mars was warmer. As the planet cooled, the lake froze solid and was covered with an insulating layer of sediment. At the same time, geothermal energy warmed the ice from below, creating a liquid layer. Thousands of years later, the weakened sediment layer suddenly collapsed, breaking the ice and letting water rush to the surface.

Until now, this scenario has only been theoretical, says Roda. “Now we have geological and hydrological evidence that this process could have occurred on Mars during its early history.”

The notion may also bode well in the hunt for signs of past life on Mars. Extreme environments on Earth can host microbes that revert to a dormant, frozen state for thousands of years only to revive when the climate warms up again. On Mars, until the ice cracked, the liquid part of the lake may have played host to hardy microbial life, which may have become dormant as the escaping water refroze in the soil.

“Maybe these outflow channels are places where these dormant organisms came into a living state and would then have gone dormant again,” says Baker. “Microbes could be waiting for us to drill a hole and sample ice and bring them back to life.”

Journal reference: Icarus, DOI: 10.1016/j.icarus.2014.03.023