It may be known as the rocky red planet, but evidence is mounting of salt water at the base of polar sediments on Mars.
Professor Graziella Caprarelli of the University of Southern Queensland is part of an international team looking at the bright reflection signals beneath the surface of Mars, which were first spotted in data obtained between 2010 and 2019 by the founder of the MARSIS radar aboard the Mars Express.
The Italian team primarily suggested that the reflections refer to a mixture of salt lakes, and they published their research in Sciences in 2018 and in natural astronomy in 2021. Recently, a new collaboration between the Italian team and researchers based in the United States provided new evidence supporting this interpretation.
The results of these studies were recently published in journals Nature Communications and the Journal of Geophysical Research: Planets.
Prof. Caparrelli said new lab experiments and simulations have ruled out alternative explanations.
“We explored questions such as ‘Can the strong radar signals be produced by other types of materials such as mud or salt ice, or by constructive interference,'” she said.
“The most recent papers address the long-standing question regarding temperatures at the base of the Antarctic cap: Until now, they were considered too low even for brines to be liquid.”
Professor Caparelli, an assistant at the University of Southern Queensland’s Center for Astrophysics, has developed thermal models and calculated the temperature range at the base of Mars’ south polar cap, below the South Polar Layered Sediment (SPLD).
“We decided to study the physical properties of the sediment itself, by modeling the propagation of radar waves through water ice and dust.”
The new calculations set the percentage of dust inclusions in the sediment to be between 5% and 12%, further adjusting the highest rate 230 K (-43 °C) for base temperature.
“Our studies show that temperature At the base SPLD calculated so far by other researchers (about 170-180 K) it has been greatly underestimated, and can instead easily reach 200 K (-73 °C) which is in the melting temperature range of perchlorine brines ‘ said Professor Caprarelli.
“New laboratory experiments conducted in the laboratories of Rome Tri University (Italy) and the Southwest Research Institute (US) further demonstrate that the physical properties of the brine at these revised temperatures are in perfect agreement with the strength of the radar signals acquired from the base of the Martian Antarctic sediment.”
Sebastien E. Lauro et al., using MARSIS signal attenuation to assess the presence of Antarctic subglacial brines, Nature Communications (2022). DOI: 10.1038 / s41467-022-33389-4
de Stellmann et al., partially saturated brines within basal ice or sediments could explain the bright basal reversals in Antarctic sediments, Journal of Geophysical Research: Planets (2022). doi: 10.1029/2022JE007398
Presented by University of Southern Queensland
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