PARIS: Mars’ ‘missing’ water is buried beneath surface, says study

PARIS: Early Mars was thought to have
enough water to cover the whole planet in roughly 100 to 1,500 meters (330 to
4,4920 feet) of ocean.

Billions
of years ago, Mars was home to lakes and oceans — but where all the water went
to transform the planet into the desolate rock we know today has been something
of a mystery.

Most of
it was thought to have been lost to space, but a new study funded by NASA
proposes that it didn’t go anywhere but is trapped within minerals in the
crust.

“We’re
saying that the crust forms what we call hydrated minerals, so minerals that
actually have water in their crystal structure,” Eva Scheller, lead author
of the new paper in Science, told AFP.

In fact,
Scheller’s model suggests anywhere between 30 – 99 percent of the initial water
remains trapped inside these minerals.

Early
Mars was thought to have enough water to cover the whole planet in roughly 100
to 1,500 meters (330 to 4,4920 feet) of ocean.

Because
the planet lost its magnetic field early in its history, its atmosphere was
progressively stripped away, and it was assumed this was how it lost its water.

But the
authors of the new study believe that while some of the water did disappear,
the majority remained.

Using
observations made by Mars rovers as well as of meteorites from the planet, the
team focused on hydrogen, a key component of water.

There are
different kinds of hydrogen atoms. Most have just one proton in their nucleus,
but a tiny fraction, about 0.02 percent, have both a proton and a neutron,
making them heavier. These are known as deuterium, or “heavy”
hydrogen.

Because
the lighter kind escapes the planet’s atmosphere at a faster rate, the loss of
most of the water to space would leave relatively more deuterium behind.

But given
how much water the planet is believed to have started with, and the current
rate of hydrogen escape observed by spacecraft, the current
deuterium-to-hydrogen ratio cannot be explained by atmospheric loss alone.

–
Permanent loss –

The
study’s authors instead say there was a combination of two mechanisms: the
trapping of water in minerals in the planet’s crust as well as the loss of
water to the atmosphere.

“Anytime
that you have a rock and it’s interacting with water, there’s a series of very
complex reactions that form a hydrated mineral,” said Scheller.

This
process, called “chemical weathering,” also takes place on Earth —
for example, in clay, also found on Mars.

But on
our planet volcanoes recycle the water back into the atmosphere. Mars, however,
doesn’t have tectonic plates, making the changes permanent.

According
to the teams’ simulations, the planet lost between most of its water between
four to 3.7 billion years ago, which means “Mars was pretty much like we
see how it is today for the past three billion years,” said Scheller.

She added
she was excited about what the Perseverance rover, which landed last month for
a multiyear science mission on the planet, might be able to contribute to the
area of research.

“The
Perseverance rover is actually going to investigate exactly these processes and
reactions that cause the sequestration of water in the crust,” she said.

The
team’s model contains multiple scenarios, which they to compare to new data
acquired by the rover.

“We
can start to say, ‘These parts of the model aren’t working right and these
parts are’ and that’s going to help us get closer and closer and closer to the
answer,” said Scheller.