Mars' Slope Channels May Have Been Created By 'Boiling' Water

A new experiment shows that dark streaks on Mars might have been created by boiling water. While it suggests that the planet may have water, it also indicates that the water may be less in quantity than thought.

Hence, speculations are that water once ran down Martian slopes each spring, although the current atmospheric pressure of the Red Planet is too low to indicate that there might be water as it would just boil.

"A good example is that of Mount Everest - the atmospheric pressure at the top of Everest is 400 millibars, as opposed to around 1,000 millibars at sea level, and therefore, water boils at 72 degrees Celsius [161 degrees Fahrenheit] rather than 100 degrees C [212 degrees F], meaning mountaineers cannot make a decent cup of tea," said Susan Conway, a planetary geomorphologist at the University of Nantes and co-author of the study. "On the Martian surface, the pressure is 5 to 10 millibars, meaning that liquid water boils no matter what the temperature is."

Earlier studies had presumed that Martian dark streaks could be from dust avalanches or the venting of carbon dioxide gas. Yet, the experiments under simulated Martian conditions show that they might be due to boiling water.

The team kept a block of ice on top of a slope that had loose, fine-grained sand. The resulting meltwater that descended was recorded.

"No one had performed such experiments before, so it was both exciting and intimidating to be able to break new ground," Conway said.

"It takes a lot of testing to find a setup which adequately reproduces Martian conditions, yet can be observed and measured easily," she added. "For example, we had the problem where the ice block we used for our source of water kept falling down the slope as it melted, destroying the features created by the seeping water. So we had to design an ice-cube safety belt, which stopped it tumbling."

Scientists realised that in the earth, flowing water would have no effect on the slope. But when they simulated a planet like Mars with low air pressures, they found that the water boiled and threw sand grains into the air, leading to the creation of slopes with small channels, just as they had seen on Mars. Moreover, the amount of water required to create the slopes was much less than thought.

"We already knew that water should boil under Martian conditions, but what we did not predict was that the boiling would be so intense where the water encountered the dry sediment," Conway said. "Our results show that a very small amount of water can actually move a disproportionately large amount of sediment, more than is possible under terrestrial conditions for the same amount of water."

The findings were published in the May 2, 2016, issue of Nature Geoscience.