In the quest to find life on Mars, scientists have found strong pieces of evidence to support the presence of flowing liquid water on the Red planet. Although they did not directly detect liquid water, they had spotted water-bearing salts in mysterious streaks called recurring slope lineae (RSL).
But it does not stop there. Now, new research conducted by the same headline-making team revealed that the mysterious, dark lines on the Martian surface have actually been caused by a process unlike anything on Earth.
Recreating Martian Conditions
On Mars, the atmospheric pressure is about 1/100th that of Earth — too low for liquid water to remain on the surface.
To better illustrate, planetary geomorphologist Susan Conway told Space.com that the atmospheric pressure on Mount Everest is 400 millibars, sea level is at 1,000 millibars, and the Martian surface is only at 5 to 10 millibars. This means that liquid water on Mars will boil no matter what the temperature is.
Conway and her colleagues recreated the same low atmospheric conditions at the Large Mars Chamber in England in order to produce accurate results. It had taken them a month of unsuccessful experiments before they found the perfect setup.
The research team placed a block of ice on top of a slope comprised of fine-grained sand, observing how the meltwater moved downhill through the sand. One problem they encountered was that the block of ice kept moving down the slope, so they had to put a safety belt to prevent it from tumbling.
Here is what happened: under Earth-like conditions, the meltwater only gushed and did not change much of the slope.
Under Mars-like conditions, however, the meltwater boiled and popped sand grains like they were popcorns, launching them airborne. The grains piled up and collapsed, then triggered avalanches.
Conway said they did not predict that the boiling water would be so intense.
"We all crowded around the chambers, going, 'Aw, that's so cool!'" said Conway.
Their results suggest that even lesser amount of water could move large piles of sediment, something that is more than possible under terrestrial conditions with the same amount of water.
The Good, The Bad And The Mysterious
The study, which is featured in the journal Nature Geoscience, offers both good and bad news.
On one hand, the findings indicate that water is a viable candidate for the formation of RSL, leaving the possibility that there is presence of liquid water at present-day Mars.
On the other, the presence of boiling water could mean that much less water is needed and the water is actually very short-lived. If so, it means the environment is not suitable for microorganisms.
But the mystery still remains. The team's study is limited in the way that they cannot actually mimic Martian gravity, and indisputable proof could only be taken by future exploration.
Ice expert Jennifer Hanley, who was not part of the study, said the research was performed at best-case temperatures for the "Martian summer," forgetting that RSLs also form all through spring at cooler temperatures.
One big obstacle to finally solving the puzzle is finding a safer way to view the RSL up close. The Mars Reconnaissance Orbiter would not have a clear enough view to observe RSLs.
What about rovers? Those are out of the equation. NASA is trying to steer the rovers away from RSLs to prevent them from contaminating the sites with traces of life from Earth. It could throw off experiments or even abet a microbiological invasion.
Meanwhile, Conway and her colleagues believe that their findings lay the groundwork for further investigations. She said another question that needs to be answered is this: if there is more water on Mars, does the boiling become swamped by erosion and transport?
One hopes the answer lies in the future.
Watch the sandgrain popping action below.