An international team of researchers has used seasonal variations to
identify likely sub-surface deposits of water ice in the temperate regions
of Mars where it would be easiest for future human explorers to survive. The
results are being presented this week by Dr Germán Martínez at the European
Planetary Science Conference (EPSC) 2021.
Using data from NASA’s Mars Odyssey, which has spent almost 20 years
orbiting the Red Planet, Martínez and his colleagues have identified two
areas of particular interest: Hellas Planitia and Utopia Rupes, respectively
in the southern and northern hemisphere. Seasonal variations in levels of
hydrogen detected suggests that significant quantities water ice can be
found in the metre or so below the surface in these regions.
Martínez, of the Lunar and Planetary Institute, said: ‘Data from Mars
Odyssey’s Neutron Spectrometer showed signs of hydrogen beneath the surface
Mars from mid to equatorial latitudes, but we still had the challenge of
working out whether this is in the form of water ice, which can readily be
used as a resource, or locked away in mineral salts or in soil grains and
minerals. This is where the seasonal variation provides an important clue.
As the coldest ground temperatures occur at the same time as the largest
observed increase in hydrogen content, it suggests that water ice is forming
in the shallow subsurface of these regions during the fall and winter
seasons, and then sublimating into gas during the warm season of each
hemisphere.’
Water ice in the shallow subsurface has been found in plentiful supply at
the poles. However, the frigid temperatures and the limited solar light make
polar regions a hostile environment for human exploration. The areas from
equatorial to mid latitudes are much more hospitable for both humans and
robotic rovers, but only deeper reservoirs of water ice have been detected
to date, and these are hard to reach.
To survive on Mars, astronauts would need to rely on resources already
available in-situ, as sending regular supplies across the 55 million
kilometres between Earth and Mars at their closest point is not an option.
As liquid water is not available in the cold and arid Martian environment,
ice is a vital resource. Water will not only be essential for life-support
of the explorers, or the growth of plants and food, but could also be broken
down into oxygen and hydrogen for use as rocket fuel.
Two other regions are rich in hydrogen: Tharsis Montes and the Medusae
Fossae Formation. However, these do not display seasonal variations and
appear to be the less accessible forms of water.
‘Definitely, those regions too are interesting for future missions,’ added
Martínez. ‘What we plan to do now for them or Hellas Planitia and Utopia
Rupes, is to study their mineralogy with other instruments in the hope of
spotting types of rock altered by water. Such areas would be ideal
candidates for robotic missions, including sample return ones, as the
ingredients for rocket fuel would be available there too.’
Reference:
EPSC2021-443: Looking for Non-Polar Shallow Subsurface Water Ice in
Preparation for Future Human Exploration of Mars
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