A recent study confirms something we have been saying for years. Mars, as well as other inner solar system bodies possess liquid water among other fluids underground. The fact that there is not liquid water on the surface is related to the very low atmospheric pressure (100 times smaller than on Earth) and frigid temperatures (average around minus 80 centigrades or less). Because of these conditions only ice and small amount of water vapour are present on the surface
However, liquid water should be present at moderate depth where there is internal heat and pressure sufficient to sustain it as a liquid.
The following is an article from Science and Astronomy where these aspects are developed.
Mars May Have Lots of Water Deep Underground
Dark
streaks known as recurring slope lineae (RSL) on the walls of Mars’ Palikir
Crater, as seen by NASA’s Mars Reconnaissance Orbiter may be evidence of liquid
water.
(Image: © NASA/JPL/University of Arizona)
The water
thought to be responsible for Mars' intriguing seasonal dark streaks may be
coming from very deep underground, a new study suggests.
These
streaks, known as recurring slope lineae (RSL), appear on some
Martian slopes during warm parts of the year. Scientists have posited
that RSL are caused by transient flows of briny water at, or just beneath, the
Red Planet's surface.
"We suggest that this may not be true," study
co-author Essam Heggy, a research scientist at the University of Southern
California (USC) and NASA's Jet Propulsion Laboratory in Pasadena, said in a
statement. "We propose an alternative hypothesis that they originate from
a deep pressurized groundwater source, which comes to the surface moving upward
along ground cracks."
And Heggy does mean deep: The aquifers feeding the RSL
likely lie about 2,460 feet (750 meters) underground, according to the new
study.
Heggy and
lead author Abotalib Z. Abotalib, a postdoctoral research associate at USC,
studied imagery captured by NASA's Mars Reconnaissance Orbiter (MRO),
which discovered RSL back in 2011. They looked specifically at three RSL-bearing
craters, as well as streaks in the huge canyon complex Valles Marineris.
Abotalib and Heggy found a spatial correlation between RSL
and tectonic and impact-related faults — features that could facilitate
the movement of water from deep underground to the surface.
The duo also modeled heat flow in the Martian subsurface and
studied underground water movement in desert regions here on Earth. These
various lines of research indicate that RSL water is probably coming from
deeply buried briny aquifers, the researchers said.
"The
experience we gained from our research in desert hydrology was the cornerstone
in reaching this conclusion," Abotalib said in the same said in the same
statement. "We have seen the same mechanisms in the North African
Sahara and in the Arabian Peninsula, and it helped us explore the same
mechanism on Mars."
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Their proposed explanation also explains the seasonality of
RSL.
"The
system shuts down during winter seasons, when the ascending near-surface water
freezes within fault pathways, and resumes during summer seasons when brine
temperatures rise above the freezing point," the researchers wrote in the
new study, which was published last week in the journal Nature Geoscience.
If Abotalib and Heggy are right, Mars' deep groundwater
system is more extensive than previously thought. Last year, Europe's Mars Express orbiter found
evidence for a big surface lake near the planet south pole, but signs of
aquifers at lower latitudes have been lacking to date.
The new study is far from the last word on RSL, however. For example, not everyone thinks the
streaks are indeed evidence of liquid water; some scientists regard dry
landslides as a more likely explanation .
And there could be more than one RSL-formation mechanism operating on
Mars, Abotalib and Heggy noted.
By Mike Wall
Science and
Astronomy
https://www.space.com/mars-deep-groundwater-recurring-slope-lineae.html
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