Article Posted on : - Nov 19, 2014

Image from NASA's Mars Odyssey spacecraft

WASHINGTON (PTI): Mars was at some point warm enough for liquid water to flow on its surface but that warmth and water flow on the Red Planet were probably episodic, according to a new study.

New research shows volcanism and greenhouse gas could have warmed the planet sufficiently, but only for tens or hundreds of years at a time.

Ample evidence of ancient rivers, streams, and lakes make it clear that Mars was at some point warm enough for liquid water to flow on its surface.

The study, by scientists from Brown University and Israel's Weizmann Institute of Science, suggests that warmth and water flow on ancient Mars were probably episodic, related to brief periods of volcanic activity that spewed tonnes of greenhouse-inducing sulphur dioxide gas into the atmosphere.

The work, which combines the effect of volcanism with the latest climate models of early Mars, suggests that periods of temperatures warm enough for water to flow likely lasted for only tens or hundreds of years at a time.

The latest generation of climate models for early Mars suggests an atmosphere too thin to heat the planet enough for water to flow.

The sun was also much dimmer billions of years ago than it is today, further complicating the picture of a warmer early Mars, researchers said.

"These new climate models that predict a cold and ice-covered world have been difficult to reconcile with the abundant evidence that water flowed across the surface to form streams and lakes," said James W Head, co-author of the new paper with Weizmann's Itay Halevy.

"This new analysis provides a mechanism for episodic periods of heating and melting of snow and ice that could have each lasted decades to centuries," said Head.

Halevy and Head explored the idea that heating may have been linked to periodic volcanism.

Many of the geological features that suggest water flow date to around 3.7 billion years ago, a time when massive volcanoes are thought to have been active and huge lava outpourings occurred.

On Earth, however, widespread volcanism often leads to cooling rather than warming. Sulphuric acid particles and thick ash reflect the sun's rays, and that can lower temperatures.

But Head and Halevy thought the effects of sulphur in Mars' dusty atmosphere might have been different.

To find out, the researchers created a model of how sulphuric acid might react with the widespread dust in the Martian atmosphere.

The work suggests that those sulphuric acid particles would have glommed onto dust particles, which would reduce their ability to reflect the sun's rays.

Meanwhile sulphur dioxide gas would produce a modest greenhouse effect - just enough to warm the Martian equatorial region so that water could flow.

The research was published in the journal Nature Geoscience.