Third of Mars once covered by ocean
A huge, potentially life-giving sea likely covered more than a third
of Mars some 3.5 billion years ago, according to a study released
Sunday.
Spread over an area the size of the Atlantic Ocean, it would have
straddled the north pole and contained the equivalent of a tenth of the
water on Earth.
For decades scientists have argued as to whether the Red Planet once
harboured bodies of water big enough to help nourish a true hydrological
cycle marked by evaporation and rainfall.
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The planet
Mars. Google |
Recent evidence suggests as much, but doubts remained.
To dig deeper, Gaetano Di Achille and Brian Hynek of the University
of Colorodo in Boulder sifted through huge stores of images collected by
NASA’s Mars Orbiter Laser Altimeter (MOLA) in the late 1990s and other
more recent European and US satellite-based monitoring systems.
The data was not new, but the researchers were the first to link up
all available information on Mars’ terrain into a single computer-driven
model.
The study, published in Nature Geoscience, found 52 river-delta
deposits scattered across the planet. More than half occurred at about
the same elevation, and thus probably marked the boundary of the
once-massive sea.
All of these would have been connected either directly to the ocean,
or to its groundwater table along with several large, adjacent lakes.
The scientists calculated that the ancient sea covered 36 percent of
the planet’s surface and contained about 124 million cubic kilometres
(30 million cubic miles) of water.
Even as single-cell life forms were emerging on our planet some 3.5
billion years ago, Mars probably had an Earth-like water cycle including
precipitation, runoff, cloud formation, ice formation and groundwater
accumulation, they conclude.
In a parallel study published in the Journal of Geophysical Research
(Planets), Hynek and colleagues catalogued some 40,000 river valleys on
Mars, four times the number previously suspected.
“The abundance of these river valleys required a significant amount
of precipitation,” Hynek said.
“This effectively puts the nail in the coffin regarding the presence
of past rainfall on Mars.” Many puzzles, however, still remain.
“One of the main questions we would like to answer is where all of
the water on Mars went,” said Di Achille.
Future Mars missions — including NASA’s 485 million dollar (400
million euro) Mars Atmosphere and Volatile Evolution mission (MAVEN),
slated for launch in 2013 — may provide clues.
The new studies also provide critical leads on where to look for
signs of early Martian life.
“On Earth, deltas and lakes are excellent collectors and preservers
of signs of past life,” said Di Achille.
“If life ever arose on Mars, deltas may be the key to unlocking Mars’
biological past.”
Hynek also noted that long-lived oceans may have provided an
environment for microbial life to take hold on Mars.
The European Space Agency (ESA) and NASA have separately forecast a
manned flight to Mars in about three decades.
The Red Planet’s distance from Earth varies between 55 million
kilometres (34 million miles) and more than 400 million kilometres.
AFP
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