Evidence suggests that Mars had water flowing on its surface at various points in its ancient history. But the evidence also points to temperatures being far too cold at those time for water to be liquid. So, how can both facts be true? At last, this paradox may be on the verge of resolution.

A new paper in Nature Geoscience posits an interesting explanation that could let both of the two contradictory facts stand together: A series of giant, incredibly active ancient Martian volcanoes exploding over 3.7 billion years ago.

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The paper, which was released from researchers at Brown University and the Weizmann Institute of Science, pays special attention to the sulfur emissions that could be released by that large-scale, coordinated spurt of volcanic eruptions. The temporary surface warming effect created by those emissions could, say researchers, result in brief periods lasting decades, perhaps even centuries, where the temperatures rose enough for the ice to thaw out during the days.

Most intriguingly of all, though is a comparison drawn by the paper's c0-author James Head between those ancient Martian thawing conditions and the conditions found in certain parts of our own Antarctic. In a statement, he noted that the sequence of events that their theory suggested on Mars, with ice thawing during the warmer days and re-freezing in the colder nights, is one we see right now in the dryer areas of the Antarctic where water can pool into temporary flowing streams during the warm seasons.

And that, says Head, has implications for how — and where — we should be looking for signs of life on Mars:

Life in Antarctica, in the form of algal mats, is very resistant to extremely cold and dry conditions and simply waits for the episodic infusion of water to 'bloom' and develop. Thus, the ancient and currently dry and barren river and lake floors on Mars may harbor the remnants of similar primitive life, if it ever occurred on Mars.

Image: ESA/DLR/Freie Universitat Berlin (G. Neukum)