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Mars May Be Habitable Today

From: Ray Dickenson <r.dickenson.nul>
Date: Mon, 25 Feb 2013 17:07:35 -0000
Archived: Tue, 26 Feb 2013 06:08:26 -0500
Subject: Mars May Be Habitable Today


Source: Space.Com


Date: 25 February 2013

Mars May Be Habitable Today, Scientists Say
Rod Pyle

LOS ANGELES - While Mars was likely a more hospitable place in
its wetter, warmer past, the Red Planet may still be capable of
supporting microbial life today, some scientists say.

Ongoing research in Mars-like places such as Antarctica and
Chile's Atacama Desert shows that microbes can eke out a living
in extremely cold and dry environments, several researchers
stressed this at "The Present-Day Habitability of Mars"
conference held here at the University of California Los Angeles
this month.

And not all parts of the Red Planet's surface may be arid
currently - at least not all the time. Evidence is building that
liquid water might flow seasonally at some Martian sites,
potentially providing a haven for life as we know it.

"We certainly can't rule out the possibility that it's habitable
today," said Alfred McEwen of the University of Arizona,
principal investigator for the HiRise camera aboard NASA's Mars
Reconnaissance Orbiter spacecraft. [The Search for Life on Mars:
A Photo Timeline]

Surface water on Mars?

McEwen discussed some intriguing observations by HiRise, which
suggest that briny water may flow down steep Martian slopes
during the local spring and summer.

Sixteen such sites have been identified to date, mostly on the
slopes of the huge Valles Marineris canyon complex, McEwen said.
The tracks seem to repeat seasonally as the syrupy fluids
descend along weather-worn pathways.

While the brines may originate underground, Caltech's Edwin Kite
noted, there is an increasing suspicion that a process known as
deliquescence - in which moisture present in the atmosphere is
gathered by compounds on the ground, allowing it to become a
liquid - may be responsible.

Astrobiologists are keen to learn more about these brines, for
not much is known about them at the moment.

"Briny water on Mars may or may not be habitable to microbes,
either from Earth or from Mars," McEwen said.

This image combining orbital imagery with 3-D modeling shows
flows that appear in spring and summer on a slope inside Mars'
Newton crater.

Hardy microbes

Martian life may be able to survive even in places where water
doesn't seep and flow, some scientists stressed.

For example, microbes here on Earth make a living in the Atacama
and the dry valleys of Antarctica, both of which are extremely
cold and arid, said Chris McKay of NASA's Ames Research Center
in Moffett Field, Calif.

Antarctic sites also receive seasonally high ultraviolet
radiation doses thanks to a hole in the ozone layer that tends
to develop every August through November. This provides yet
another parallel to Mars, whose thin atmosphere and lack of a
protective magnetic field make the planet more radiation-
bombarded than Earth.

In the Antarctic dry valleys, McKay said, organisms dwell within
rocks, just deep enough to be shielded from the worst of the UV
but close enough to the surface to receive the benefits of
photosynthesis. Something similar might be happening on Mars
today, if life ever evolved there.

McKay also discussed deliquescence, which in the Atacama allows
salts to gather enough water to support the existence of life.

McKay offered some advice to NASA's Mars rover Curiosity, which
landed in August to determine whether Mars could ever have
supported microbial life: "Watch for salt along the road!"

A possible energy source

NASA's Curiosity rover found evidence for an ancient, flowing
stream on Mars at a few sites, including the rock outcrop
pictured here, which the science team has named "Hottah" after
Hottah Lake in Canada's Northwest Territories. This image mosaic
was taken by Curiosity's 100-millimeter Mastcam telephoto lens
on its 39th Martian day, or sol, of the mission (Sept. 14, 2012
PDT/Sept. 15 GMT).

View full size image

A number of presenters spent some time talking about
perchlorate, a chlorine-containing chemical that NASA's Phoenix
lander spotted near the Martian north pole in 2008.

McKay and other researchers think perchlorate may be the reason
that NASA's twin Viking landers didn't detect any organic
compounds - the carbon-containing building blocks of life as
we know it - on the Red Planet back in the 1970s.

The Vikings vaporized Martian soil and looked for any organics
boiling off. They found nothing but a few chlorine compounds
that were attributed to contamination. But after Phoenix's
perchlorate find, McKay and some other researchers performed an

They added perchlorate to some desert dirt from Chile known to
contain organics. They heated the soil up and found the same
chlorine compounds the Vikings did, suggesting that organics may
have been present in the Vikings' samples but were broken down
by the combination of heat and perchlorate.

While this backstory is interesting in its own right,
perchlorate is also relevant to the possible habitability of
present-day Mars.

"Perchlorate, it turns out, is a potent chemoautotrophic energy
source," said Carol Stoker, also of NASA Ames, noting that the
chemical could potentially sustain microbes in the dark Martian
subsurface, where photosynthesis is not an option.

And some Earth microbes use perchlorate for food, so that could
be happening on Mars as well, scientists have pointed out.

"The Present-Day Habitability of Mars" took place Feb. 4-5 and
was co-hosted by the NASA Astrobiology institute and the UK
Centre for Astrobiology. Archived videos of conference
presentations are available here.



Ray D

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