An international team from France, Britain and the United States has reported Monday that the results of their Earth-bound lab experiments back up the theory that seasonal dark lines on Mars are created by water. They had constructed models and simulated Martian conditions in an attempt to follow up a 2015 study which had found “the strongest evidence yet” for liquid water on Mars. However, because of the low pressure of the Red Planet's atmosphere, water cannot survive long in liquid form, as it either boils or freezes.
In September 2015, a report was
published in Nature Geoscience that concluded that the lines on
Martian slopes may be streaks of super-salty brine. The report said
that evidence had been found in the lines of “hydrated” salt
minerals, which require water for their creation.
The lines are
typically under five metres wide and range up to a few hundred metres
in length and appear on the slopes during warm seasons. They then
lengthen and fade as they cool down.
"Under certain circumstances, liquid water has been found on Mars," NASA concluded at the time. For the latest study, also published in Nature Geoscience, researchers took to the lab to try and explain how water could have made the lines.
The team, led by Marion Masse of the University of Nantes in France, included several of the authors of last year's headline-making study.
They placed a block of ice on a 30-degree plastic slope covered with loose fine-grained sand, and allowed it to melt in a chamber in which Martian pressure and summer temperature was recreated.
They repeated the experiment under Earth conditions to compare the processes.
Under Martian pressure, they found, melting ice produced a liquid which boiled vigorously as it flowed downslope and filtered into the sand.
The evaporating water vapour blasted grains upward, creating ridges which collapse onto themselves when they become too steep, forming channels.
"The morphologies produced on the sandy slopes in these experiments are remarkably similar to the streaks observed on Mars," Wouter Marra of the geosciences faculty of the University of Utrecht in the Netherlands commented on the study.
"This process in which unstable boiling water causes grains to hop and trigger slope failures may underlie some of the active landforms observed on the Martian surface."
