Mars Had Been Wet, Scientists Deduce by Shocking a Rock

Mars, not the Red Planet but the Blue one? Mineral in Martian meteorites turns out to be water-rich whitlockite violently shocked into losing its hydrogen.

Mount Sharp on Mars.
Mount Sharp on Mars. AP

Could Mars once have been not the Red Planet, but the Blue one?

Sometimes pieces of rock from Mars land on Earth. There is a mineral commonly found in these Martian meteorites called merrillite, that does not exist on Earth.

Now, another kind of mineral found on Mars, and also rarely on earth, is called whitlockite. It is an unusual form of calcium phosphate. Whitlockite contains hydrogen atoms, merrillite does not. (Water consists of hydrogen and oxygen atoms.)

Scientists at the University of Nevada created a synthetic version of whitlockite, complete with hydrogen. Then they conducted shock-compression experiments on their ersatz whitlockite, aping the violence with which meteorites get ejected from Mars. That can happen for instance when a meteor hits the planet, causing bits of rock to get blown into outer space.

They found that shocked whitlockite dehydrates and turns into – merrillite.

In other words, the Martian rocks could have originally had whitlockite, not merrillite. And that in turn means that Mars may have been a wetter place than had been thought, according to the international study, which was done in part at the Department of Energy's Lawrence Berkeley National Laboratory. The study was published in the journal Nature Communications.

"If even a part of merrillite had been whitlockite before, it changes the water budget of Mars dramatically," explained Oliver Tschauner of the Department of Geoscience at the University of Nevada.

Whitlockite also contains phosphorous, an essential element for life on Earth. What all this boils down to is that once upon a time, Mars could have been wet, even very wet, and had conditions appropriate for the development of life.

The planet could even have been covered in water – we don't know.

It bears adding that the shock experiments generated pressures and temperatures that are a wee fraction of the stresses created by cosmic violence, lasting for only about 100 billionths of a second, a fraction as long as an actual meteorite impact. But if the tests created even partial conversion to merrillite, a real impact would likely have produced "almost full conversion" to merrillite, Tschauner said.

Since we're obsessed with aliens, especially from next-door Mars, water on the neighboring planet has been the subject of much scientific attention. There are signs that water does flow on Mars: In 2013, scientists reported darkish streaks on Martian slopes that they think could be flows of water resulting from changing temperatures. And last November, NASA reported a huge underground body of water ice on Mars, in one area.

100 meter-long streaks flowing downhill on Mars are inferred to have been formed by contemporary flowing water.
AFP Photo/NASA/JPL/University of Arizona

"The only missing link now is to prove that (merrillite) had, in fact, really been Martian whitlockite before," Tschauner said. "We have to go back to the real meteorites and see if there had been traces of water."

Or go to Mars, collect some rocks and bring them home.

These inclined beds of sandstone on Mars are thought to be deposits of small deltas fed by rivers flowing down from the crater rim to the north, forming a lake to the south, where Mount Sharp is now.

How does one identify a meteorite from Mars, anyway? Chemical analysis. The rock's chemical and mineral composition is atypical for Earth, and typical for Mars. If they aren't from Mars, they are from a planet exactly like it, scientists concede.