Yahoo – AFP,
Mariette Le Roux with Jean-Louis Santini in Washington, 28 Sep 2015
 |
An image
made available by NASA on September 27, 2015 shows dark, narrow,
100 meter-long
streaks called recurring slope lineae flowing downhill on Mars,
inferred to
have been formed by contemporary flowing water (AFP Photo)
|
Paris (AFP)
- Scientists announced Monday "the strongest evidence yet" of liquid
water on Mars, raising the distant prospect of microscopic life on our
neighbouring planet.
Curious
lines running down steep slopes on the surface of the Red Planet may be streaks
of super-salty brine, a team said.
Evidence of
"hydrated" salt minerals in the streaks "strongly support the
hypothesis" of liquid water on Mars -- though not H2O as we know it,
concluded a research paper in the journal Nature Geoscience.
 |
Image
captured by NASA's Hubble
Space Telescope shows Mars
(AFP Photo)
|
NASA said
the findings, made with its Mars Reconnaissance Orbiter, "provide the
strongest evidence yet that liquid water flows intermittently on present-day
Mars."
"Mars
is not the dry, arid planet we thought of in the past," Jim Green, the
American agency's planetary science director told journalists in Washington.
The
presence of hydrated salt minerals in the lines, indicates that "water
plays a vital role in the formation of these streaks," according to
Lujendra Ojha of the Georgia Institute of Technology in Atlanta, who
co-authored the study.
The
minerals, called perchlorates, contain water molecules in their make-up.
It is
widely accepted that the Red Planet once hosted plentiful water in liquid form,
and still has water today, albeit frozen in ice underground.
Earlier
this year, NASA said almost half of Mars' northern hemisphere had once been an
ocean, reaching depths greater than 1.6 kilometres (one mile).
Anybody
out there?
Astrobiologist
Lewis Dartnell of the University of Leicester Space Research Centre said the
study, which he did not take part in, presented "very strong evidence that
what we believe to be signs of liquid water trickling down the Martian surface
is in fact that."
This, in
turn, raised the intriguing prospect of life, he told AFP.
"If
there is liquid water trickling beneath the surface, maybe that's an
environment where bacteria and microbial life can survive... The results we've
had this afternoon are very exciting because they increase the possibility that
there is life alive on Mars today."
Others said
it was early days yet.
"It's
a smoking gun: Liquid water hasn't been seen directly in these 'dark stains',"
Mark McCaughrean, senior science advisor at the European Space Agency, told
AFP.
 |
A handout
image made available by NASA on September 27, 2015, shows
dark, narrow, 100
meter-long streaks called recurring slope lineae flowing downhill
on Mars,
inferred to have been formed by contemporary flowing water (AFP Photo)
|
"Rather,
they've spotted the kind of hydrated minerals that could make water briny
enough to enable it to flow as a liquid at the extremely low, sub-zero
temperatures on Mars. That makes the hypothesis that liquid water is involved
in making those stains quite plausible, but isn't really a direct
detection."
And even if
briny water does exist: "whether or not that substantially improves the
chances of us finding life on Mars... the jury is definitely still out on
that," McCaughrean added.
Scientists
have long hypothesised that the seasonal streaks dubbed "recurring slope
lineae" (RSL), may be formed by brine flows.
But
spacecraft images have been unable to reveal detail of what exactly is in the
lines -- the pixel resolution is coarser than the width of the streaks
themselves.
Up to a few
hundred metres in length and typically under five metres (16 feet) wide, they appear
on slopes during warm seasons, lengthen, then fade as they cool.
For the new
study, a team from the United States and France devised a method to extract
more data from individual pixels in images from the CRISM spectrometer on
NASA's Orbiter, and detected evidence of hydrated salt minerals in the streaks.
"Today
we're revolutionising our understanding of this planet," said Green.
"Our rovers are finding there's a lot more humidity in the air" and
the soil is moister than anticipated.
 |
An image
made available by NASA shows dark narrow streaks called recurring
slope lineae,
hypothesized to be formed by flow of briny liquid water, emanating
out of the
walls of Garni crater on Mars (AFP Photo)
|
Added
Michael Meyer, lead scientist for NASA's Mars exploration programme: "It
seems that the more we study Mars, the more we learn how life could be
supported and where there are resources to support life in the future."
This was
not the first time perchlorates were found on Mars.
In April
this year, a different team wrote in the same journal that perchlorate salts
were "widespread" on the surface of our neighbouring planet, and
humidity and temperature conditions were just right for salty brines to exist.
Perchlorates
are highly absorbent and lower the freezing point of water so that it remains
liquid at colder temperatures.
Asked if
the data was the final proof of liquid water on Mars, McEwen replied: "I
would say almost."
"Strongest evidence yet" of liquid water on Mars, NASA says http://t.co/AuHWU3cjed pic.twitter.com/qSFurJ40aL
— Agence France-Presse (@AFP) September 28, 2015
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