Volcanic eruptions could provide enough heat so that liquid water periodically seeps into the ancient Martian surface, suggests a new study.
The new findings, presented in Nature Geoscience, may explain the discrepancies between climate models, showing that Mars was never able to have liquid water on its surface, and the clear geological imprints left by the seas and rivers that were formed due to the flow of water.
"There is incontrovertible evidence that Mars was once warm enough to have liquid water on its surface," says one of the authors of the study, Professor James Head of Brown University in Providence, Rhode Island.
"It's pretty difficult to compare this fact with the latest climate models, showing that Mars has always been very, very cold, with too thin an atmosphere, not capable of sufficiently heating the planet so that water can be present on the surface in liquid form," he added.
The leader and lead author of the study, Dr. Itay Halevy from the Weizmann Institute in Tel Aviv, discovered tremendous volcanic activity on Mars about 3, 7 billion years ago, at the same time as water flowed along the surface of the Red Planet, forming river valleys, deltas and lakes . Significant volcanic eruptions on Earth could have caused cooling rather than warming, since particles of sulfuric acid and a thick plume of ash either absorbed solar radiation or reflected it back into space, lowering the temperature at the surface.
But the dust in the atmosphere of Mars softens the effect of cooling, says the head.
"We assume that the early atmosphere of Mars was rather dusty, and our calculations show that a large number of volcanic minerals, such as sulfur dioxide and sulfuric acid, could hold these dust particles, reducing their ability to reflect the sun's rays," he explains.
The authors found short periods of intense volcanic activity, during which a significant level of greenhouse inducing gaseous sulfur dioxide erupted into the atmosphere, thereby heating the Martian equatorial region enough for it to flow liquid water.
"According to our calculations, during these short periods about 30 percent of the surface of Mars was covered with lava flows."
"If you raise the temperature above zero for several decades to centuries, it will give enough heat to melt ice and snow, and geological features that we see in the Martian valleys and lake basins formed," says the manager. Itai Halevy believes that the climate of early Mars could have some similarities with the cold, desert valleys of McMurdo, which he studied in Antarctica.
“The average annual temperature in the Antarctic dry valleys is below zero, but the peak summer temperature in the daytime can exceed the melting point of ice, forming streams that later freeze again,” Halevy says.
"In the same way, we see that volcanism could raise the temperature in the early climate of Mars above the melting point for centuries, causing episodic periods of water flow and lake formation."
The new study may provide new clues about where to look for fossil remains of any life forms that hypothetically could once have existed on Mars.