U.S. Water News Online
WASHINGTON -- Mars is now dry, dusty and cold, but a new
study confirms that the Red Planet once was covered by vast oceans
and had more water per square mile than Earth.
In fact, it once had enough water to cover the planet to a depth
of almost a mile, researchers say, citing an analysis of data
measuring the amount of molecular hydrogen in the atmosphere.
Unlike Earth, Mars lost its water over millions of years through a
combination of chemical reaction and the bombardment of asteroids and
There is much evidence now that Mars had an ocean of liquid water,
said Vladimir A. Krasnopolsky of Catholic University of America. "But
the climate changed. ... Mars became a cold desert."
Krasnopolsky said the proven abundance of water in Mars' early
history "improves the prospects" that life could have evolved there.
In a study appearing in the journal Science, planetary
researchers Krasnopolsky and Paul D. Feldman of Johns Hopkins
University said that Mars' upper atmosphere contains molecular
hydrogen, or H2, a finding that confirms earlier theoretical models
of the water history of the planet.
The H2 comes from a chemical reaction, called dissociation, that
split the hydrogen from water, H20, and allowed the lighter hydrogen
to escape to the atmosphere.
"It is a complex chemistry process of which we are detecting only
one piece," the molecular hydrogen, said Feldman. But these findings
help to support earlier estimates of the amount of water once on
Donald M. Hunten, an expert on planetary atmospheres at the
University of Arizona, Tucson, said the studies by Krasnopolsky and
Feldman make an important contribution because they strengthen
earlier theories of Mars' water history.
"This is an observational confirmation of a theoretical model,"
said Hunten. "I am happy to see such a confirmation."
The Krasnopolsky and Feldman study is based on data from the Far
Ultraviolet Spectroscopic Explorer, a spacecraft that can detect and
identify chemicals in the atmosphere of the distant planets. The data
is the first to detect molecular hydrogen in the atmosphere of Mars.
Krasnopolsky said the findings support this scenario of Mars'
The planet was formed about 4.6 billion years ago and during its
early history had enough water for an ocean about a mile deep. Much
of this water, however, was chemically bound to the rocks and soils
of the planet. This material was rich in iron. Krasnopolsky said that
over a 300 million year period, the water reacted with the iron,
releasing molecular hydrogen to the atmosphere in a process called
"There was a massive escape of molecular hydrogen and the loss of
water was very rapid," he said. The iron-water reaction, said
Krasnopolsky, helped turn Mars into its rusty-red color.
At about 3.6 billion years ago, Mars, along with Earth, underwent
a massive bombardment from asteroids and comets. For millions of
years, rocks, some of them mountain-sized and bigger, rained down on
the planets from space.
The pounding of Mars stripped away most of its atmosphere, leaving
a thin layer of gas, mostly carbon dioxide, surrounding the planet.
Hunten said this did not happen on Earth because it is bigger than
Mars and has a stronger gravitational pull, allowing Earth to keep
its denser atmosphere.
After the pounding, Mars cooled and another phase of water loss
Sunlight, teamed with the thin atmosphere, triggered a complex
chemical reaction that ultimately resulted in an increased abundance
of molecular hydrogen in the atmosphere -- a chemical species that
was detected by the FUSE spacecraft and analyzed by Krasnopolsky and
Krasnopolsky said the water lost from Mars would have been enough
to cover the planet to a depth of about 90 feet.
He said there still is water on Mars, but it is either liquid deep
in the soil or ice. Krasnopolsky estimated that the Martian polar ice
caps contain enough water to flood the planet to an average depth of
about 45 feet.
The amount of water left on the planet is unknown, but photos from
spacecraft orbiting Mars clearly show erosion furrows cut recently by
water flow. Some experts believe that underground reservoirs
occasionally break through ice dams and carve gullies down the sides
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