With multiple successful, unmanned missions to Mars in the last decade, we’ve learned a lot more about the red planet. But one mystery that’s been difficult to reconcile is that Mars is too cold for water to flow as a liquid, and yet there is clear evidence of exactly that having happened at some point in the past. The answer could be volcanic activity heating up the planet’s surface, but maybe not in the way you would think.

Volcanic activity mars

Volcanic activity would have altered the atmosphere, temporarily allowing water to flow

Brown University geologist James Head and Itay Halevy of the Weizmann Institute in Tel Aviv have found evidence that as much as 30% of Mars’ was ‘resurfaced’ by lava some 3.7 billion years ago. But it’s not the lava flows themselves that would have been responsible for melting the ice, but the changes that volcanic activity caused in the atmosphere.

“We looked at Mars’ early atmosphere being dusty, and our calculations suggest a lot of the [volcanic plume] minerals like sulfur dioxide and sulfuric acid will adhere to these dust particles, reducing their ability to reflect the Sun’s rays, delaying cooling,” said Head, ABC reports.

This temporary change to Mars’ atmosphere may only last a few decades or centuries before the effect dissipates, but during that time at least part of Mars would become warm enough for water to melt forming temporary rivers and lakes, explaining the surface features that have been found that point to large bodies of water in the planet’s past.

Mars may have been in full bloom in the distant past

But what’s even more interesting than reconciling what we know (or think we know) about Mars’ past, is the idea of algal blooms that would have only sprung up during these rare periods of volcanic activity.

“Microbial algae matts in Antarctica are resistant to the solar radiation and extreme cold and dry conditions,” says Head. “They sit there and just wait for the water to come, and when the water does come, they burst into bloom, so to speak. At other times they just dry up and get blown about to new locations by the wind where they wait for more water.”

He speculates that the same could be true on Mars. There could have been some extremely hardy forms of life that subsisted while Mars was cold and dry, and would flourish as water flowed. If the theory is true, hopefully one of the Mars rovers will find evidence of ancient alien life after all.