The role of water in carving the planet’s surface may not be insignificant afterall.
The role of liquid water on Mars in shaping the planet’s terrain has been considered fairly insignificant because water tends to only exist in small quantities as a boiling liquid, and usually only during the warmest time of day in the summer months.
However, according to an international team of scientists, even though the water that emerges onto the surface of Mars immediately begins to boil, it creates an unstable turbulent flow that can eject sediment and cause dry avalanches. This means that even small amounts of boiling liquid water can significantly alter the Martian surface.
Here on Earth, water boils at 100 degrees Celsius (212 degrees Fahrenheit) at sea level. But its boiling point depends on atmospheric pressure—a higher altitude means a thinner atmosphere, and therefore a lower boiling point. For example, at the top of Mount Everest, water boils at 60 degrees Celsius (140 degrees Fahrenheit), but on Mars where the atmosphere is much thinner than on Earth, it can boil at temperatures as low as 0 degrees Celsius (32 degrees Fahrenheit).
During the Martian summer, temperatures can reach 20 degrees Celsius (68 degrees Fahrenheit), and when the subsurface water ice, or even the salty water discovered last year, begins to melt and emerges at the surface, the water immediately starts to boil.
So can this evaporating liquid alter Mars’ terrain?
In an attempt to answer that question, two teams, one from the Open University (UK) and the other from the GEOPS laboratory (CNRS/Université Paris-Sud), carried out the exact same experiments. The only difference was that one used a former diving decompression chamber to reproduce the low pressure of the Martian atmosphere, while the other used a cold chamber at Earth’s atmosphere. In both chambers, a block of pure ice, following by one of saline water ice, were melted at a temperature of 20 degrees Celsius on a sand-covered slope.
Comparison of the morphologies formed by the flow of liquid water on Earth (Terre) and on Mars. Photo credit: Marion Massé
Surprisingly, the results of the experiments were extremely different. Under Earth conditions, the water gradually seeped into the sand, leaving no trace on the surface after drying. However, in the Martian chamber, the water produced by the melting ice started to boil as soon as it reached the surface, and the gas that was released caused the ejection of sand grains. These grains formed small ridges at the front of the flow, and as they slowly grew larger, they became unstable and produced dry sand avalanches.
This ejection process was not as violent in the saline water experiment. However, since saline water is more viscous, it can carry sand grains and form small channels—a process that can sometimes become explosive under very low pressures.
The findings, published in the journal Nature Geoscience, provide new insight into the effect of the flow of water on Mars and how its role in shaping the Martian terrain is far from insignificant.
Detecting water on Mars is currently done by identifying morphologies similar to those produced on Earth, such as channels, gullies, or the appearance of dark traces caused by a dampened surface. However, the results of the experiments show that the morphologies produced under Martian conditions are very different, so a direct comparison between landforms produced on Earth and Mars may not be the best method for detecting the presence of water.
Water may be located in more areas than scientists currently recognize, which means life could still be hiding somewhere under the Martian surface.
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