Scientists are confused by the data about lakes on the Planet Mars.
REPUBLIKA.CO.ID, JAKARTA — In 2018, scientists made a discovery that changed the understanding of the planet Mars. Radar signals reflected just below the planet’s surface reveal ‘little gleaming patches’ indicating the presence of an underground lake on the Martian surface.
Reported from Science Alert, Sunday (27/6), though Mars has water in the form of ice, so far not a drop of liquid has ever been found on Mars.
According to the new analysis, which has found dozens more of these tiny shiny pieces, some of which are in areas too cold for clear water, even salt water, which can have lower freezing temperatures than fresh water.
“We’re not sure whether these signals are liquid water or not, but they appear to be much broader than what the original paper found,” said planetary scientist Jeffrey Plaut of NASA’s Jet Propulsion Laboratory.
“Either liquid water is common under Mars’ south pole, or this signal suggests something else.”
In 2018 scientists discovered the first lake feature. The first features were discovered at Mars’ south pole, beneath the ice sheet, using the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on the Mars Express orbiter.
A follow-up search of the archived data revealed three of these lake-like features. MARSIS uses radar signals to probe beneath the Martian ice sheet, which consists of alternating layers of carbon dioxide and water ice.
We know, from the use of such technology on Earth, which signals indicate a particular material.
“Some materials reflect radar signals better than others, and liquid water is one ‘matter’. Therefore, when the signal coming from below the surface is stronger than reflected by the surface, we can confirm that we are in the presence of liquid water,” planetary scientist Graziella Caparelli from the University of Southern Queensland in Australia told Science Alert last year.
The signal coming from this small piece of subsurface is indeed stronger than the signal coming from the surface itself. However, the area where they are found is relatively small.
So Plaut and planetary scientist Aditya Khuller of Arizona State University expanded their search. They mapped 44,000 measurements over 15 years of MARSIS data to cover the entire south pole of Mars.
They found dozens of tiny, highly reflective pieces scattered over a greater range than previously identified. But the surface of some of the new small pieces lies nearly a kilometer or more (less than a mile) below the surface, where the point temperature is estimated to be around 210 Kelvin -63 degrees Celsius.
Previous research has found that water containing calcium and magnesium salts can remain liquid at temperatures as low as 150 Kelvin for very long periods of time. Mars is rich in calcium and magnesium salts, as well as sodium. However, a 2019 paper found that there isn’t enough salt to melt the ice at the bottom of the layered deposits of Mars’ south pole.
They concluded that there needed to be some form of basaltic warming, perhaps in the form of geothermal activity: volcanism. However, while there is recent evidence of volcanic activity on Mars, it lies at lower latitudes, not the poles.
“They found that it would take twice the estimated flow of geothermal heat from Mars to keep this water liquid. One possible way to get this amount of heat is through volcanism,” Khuller explained.
“However, we haven’t really seen strong evidence for recent volcanism at the south pole, so it seems unlikely that volcanic activity would allow subsurface liquid water to be present throughout this region,” he said.
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