Liquid water beneath Martian south polar cap?
Geophysical radar reflections, laboratory experiments point to slushy
brines

Date:
January 25, 2022
Source:
Southwest Research Institute
Summary:
Scientists measured the properties of ice-brine mixtures as cold
as -145 degrees Fahrenheit to help confirm that salty water likely
exists between grains of ice or sediment under the ice cap at Mars'
south pole.

Laboratory measurements support oddly bright reflections detected
by the MARSIS subsurface sounding radar aboard ESA's Mars Express
orbiter.



FULL STORY ==========================================================================
A Southwest Research Institute scientist measured the properties of
ice-brine mixtures as cold as -145 degrees Fahrenheit to help confirm
that salty water likely exists between grains of ice or sediment under
the ice cap at Mars' south pole. Laboratory measurements conducted by SwRI geophysicist Dr. David Stillman support oddly bright reflections detected
by the MARSIS subsurface sounding radar aboard ESA's Mars Express orbiter.


==========================================================================
With a 130-foot antenna, MARSIS flies over the planet, bouncing radio
waves over a selected area and then receiving and analyzing the echoes
or reflections. Any near-surface liquid water should send a strong bright signal, whereas the radar signal for ice and rock would be much smaller.

Because conventional models assume the Mars south polar cap experiences temperatures much lower than the melting point of water, many scientists
have questioned the presence of liquid water. Clay, hydrated salts and
saline ices have been proposed as potential explanations for the source
of the bright basal reflections. The Italian-led team investigating the proposed phenomena used previously published data, simulations and new laboratory measurements.

"Lakes of liquid water actually exist beneath glaciers in Arctic and
Antarctic regions, so we have Earth analogs for finding liquid water
below ice," said Stillman, a specialist in detecting water in any
format -- liquid, ice or absorbed -- on planetary bodies and co-author
of a paper describing these findings. "The exotic salts that we know
exist on Mars have amazing 'antifreeze' properties allowing brines to
remain liquid down to -103 degrees Fahrenheit. We studied these salts in
our lab to understand how they would respond to radar." Stillman has
over a decade of experience measuring the properties of materials at
cold temperatures to detect and characterize subsurface ice, unfrozen
water and the potential for life throughout the solar system. For this
project, Stillman measured the properties of perchlorate brines in an
SwRI environmental chamber that produces near-liquid-nitrogen temperatures
at Mars-like pressures.

"My Italian colleagues reached out to see if my laboratory experiment
data would support the presence of liquid water beneath the Martian ice
cap," Stillman said. "The research showed that we don't have to have
lakes of perchlorate and chloride brines, but that these brines could
exist between the grains of ice or sediments and are enough to exhibit
a strong dielectric response. This is similar to how seawater saturates
grains of sand at the shoreline or how flavoring permeates a slushie,
but at -103 degrees Fahrenheit below a mile of ice near the South Pole
of Mars." The search for water in the cosmos is rooted in searching
for potential habitability, because all known life requires water.

"In this case 'following the water' has led us to place
so cold that life as we know it couldn't flourish,"
Stillman said. "But it's still interesting, and who knows
what evolutionary paths extraterrestrial life may have taken?" ========================================================================== Story Source: Materials provided by Southwest_Research_Institute. Note:
Content may be edited for style and length.


========================================================================== Related Multimedia:
* Mars_south_polar_cap ========================================================================== Journal Reference:
1. Elisabetta Mattei, Elena Pettinelli, Sebastian Emanuel Lauro,
David E.

Stillman, Barbara Cosciotti, Lucia Marinangeli, Anna Chiara
Tangari, Francesco Soldovieri, Roberto Orosei, Graziella
Caprarelli. Assessing the role of clay and salts on the origin of
MARSIS basal bright reflections.

Earth and Planetary Science Letters, 2022; 579: 117370 DOI:
10.1016/ j.epsl.2022.117370 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220125124026.htm

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