Another cause that the presence of liquid water would be at the origin of the reflections at the south pole of Mars

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Another cause that the presence of liquid water would be at the origin of the reflections at the south pole of Mars

In 2018, scientists from the European Space Agency (ESA) working with orbiter data Mars Express announced that they had discovered something interesting at the Martian south pole. They observed a radar signal which could be interpreted as proof of the presence of liquid water. The signal consisted of mysterious reflections from the region called Ultima Scopuli. Today, other researchers suggest another cause behind these reflections, and it has nothing to do with the presence of water.

According to the scientists behind a study published last September 28 in the journal Nature Astronomy, the signal would not come from ice or liquid water. It would rather be product of the underlying geological layers made of minerals and frozen carbon dioxide. Especially, the thickness of these layers would be the origin of the reflectionsnot the materials with which they are made.

Layers of ice near the Martian south pole
Credits NASA/JPL-Caltech/University of Arizona

The researchers used the instrument’s radar data MARSIS or Mars Advanced Radar for Subsurface and Ionosphere Sounding of the Mars Express orbiter to find the origin of the reflections. They also used computer simulations to see how different types of layers react to light.

You don’t need water to have reflections

At the Martian south pole, there is a large amount of frozen carbon dioxide. That’s why Dan Lalich, a planetary scientist at Cornell University and lead author of the study, didn’t miss to include layers of this ice in the simulations. One simulation in particular, with a layer of carbon dioxide ice placed on top of a layer of water ice, revealed that the separation and thickness of the layers determined the intensity of the reflection.

In previous studies, Lalich had already discovered that some minerals could also produce a similar reflection. According to him, even layers of ice obscured by dust from the planet Mars can produce it. It means that the presence of liquid water is not necessary to create such a reflection.

The meaning of this discovery

Lalich explains that the objective of this study was to show that the composition of the basal layers is less important than the thickness and the separation of these different layers. However, these results do not mean that there is no possibility of finding liquid water on Mars.

According to Lalich, none of the work they have done disproves the existence of liquid water in the soil of Mars. They just think that the interference hypothesis fits the observations better.

To be able to really confirm the existence of liquid water on Mars, it would be necessary to drill holes on the planet. Maybe one day astronauts will be able to land there and check it out for themselves.


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