Confirmed the presence of salty liquid water under the south polar cap of Mars

A new study conducted by an Italian-American team which includes Francesco Soldovieri, director of the CNR Institute for Electromagnetic Sensing of the Environment, and published in Nature Communications, confirms the hypothesis - put forward for the first time in 2018 – of the presence of liquid salt water in the subsoil of the Red Planet.

Figure1The discovery of the presence of salt water under the southern polar cap of Mars, made possible thanks to an investigation conducted with the Italian ASI MARSIS radar mounted on board ESA's Mars Express mission, dates back to 2018. The study, carried out by an entirely Italian research team, which also included the Institute for Electromagnetic Sensing of the Environment of the National Research Council (IREA-CNR), was published in the prestigious scientific journal Science.

Two years later another study, published in Nature Astronomy by a multidisciplinary team composed of thirteen researchers including physicists, geologists and engineers, among them Francesco Soldovieri of the IREA-CNR, confirmed the discovery by providing further proof of the existence of saltwater lakes trapped under the ice of the Martian South Pole.

A new study, published on September 28 in Nature Communications by an Italian-coordinated international team, provides now further evidence of the existence of liquid water under the south pole of Mars. In particular, the study was coordinated by the University of Roma Tre and the Institute of Radioastronomy of the National Institute of Astrophysics, with the participation of IREA-CNR together with the University of Southern Queensland (Australia), Southwest Research Institute (USA ) and Planetary Science Institute (USA).

The research concerned the southern Martian polar deposits (the so-called SPLD - South Polar Layered Deposits). The in-depth study and evaluation of the attenuation of the radar signal in the SPLD ice, already detected in the area investigated in the second study, has allowed us to arrive at two important results.

The first is that the attenuation of the MARSIS signal is constant in the entire analyzed region, thus confirming the compositional homogeneity of the polar deposits at the observation scale of the MARSIS radar.

In addition, the estimated attenuation values made it possible to recalculate the value of the reflection coefficient underlying the SPLDs and estimate the relative dielectric permittivity, equal to 40 in the highly reflective area, a situation compatible only with the presence of salt water.

Finally, starting from the estimated attenuation it was possible to obtain important information in terms of dust content in the polar deposits (SPLD), between 5 and 12%, and that the temperature at the base of the SPLD calculated so far had been underestimated. It can easily reach 200K (-73 ° C), ensuring conditions compatible with the presence of salt water in the liquid state. 

The set of the results mentioned above, therefore, confirms the presence of salt water at the base of the SPLD as the sole cause of the strong basal reflections in the Ultimi Scopuli region.


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