Warm and wet ancient Mars? Maybe not

Artist illustration of what Mars may have looked after formed, where the clay-rich areas (blue and green) are mixed with basalt lava and impact-melted rock (brown and black).

(Kevin Cannon)

Ancient Mars may not have been all that warm and wet.

The Red Planet has widespread deposits of clay minerals, which are formed through the interaction of volcanic rock and water. This fact has led some researchers to suspect that there is liquid water covers a large part of the martian surface for long stretches a long time ago — perhaps during the Noachian period, which lasted from about 4.1 billion to 3.7 billion years ago.

But a new study suggests that this clay could have formed, even longer ago, just after the planet’s formation — the significance of the Noachian is also a moderate fall of snow and chilly time, as other scientists have proposed. [The Life on Mars Search: Photo Time Line]

“This is a very controversial issue and the debate,” said study lead author Kevin Cannon, who is now a postdoctoral researcher at the University of Central Florida, but conducted the study while a Ph. D. student at Brown University in Rhode Island.

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“I would say, now, it is a kind of leaning more in the direction of the idea that Mars was mostly cold and dry during that time, and that you just had to this 100-or 1000-year periods where the temperature got a little hotter — enough to melt and flow, but maybe not enough to be a significant change of the crust and the shape of a bunch of clay and stuff like that,” said Cannon

An old bath?

Cannon and his colleagues proposed a new formation scenario for Mars’ ancient clay: that most of them took shape during the first few tens of millions of years of the planet.

In those early days, Mars was probably under a scorching hot ocean of liquid rock (like the other rocky planets, including the Earth), scientists say. If this rock is melted, the released water vapor, carbon dioxide, and other gases, the generation of a sizzling, superhot, high-pressure atmosphere on the Red Planet.

The study team synthesized rock similar to Martian basalt, is exposed, the stuff to the steam-bath conditions that probably prevailed on the Red Planet’s surface way back when. After a short two weeks, the researchers found, a lot had happened.

“It was really remarkable how quickly and extensively this basalt was altered,” Cannon said in a statement. “At the highest temperatures and pressures, ate completely through the basalt particles. It is really an intense degree of change.”

The steam atmosphere may have lasted up to 10 million years long enough to make a global layer of clay 1.9 miles (3 kilometres thick, the researchers said. So they modeled what would happen to such a layer in the subsequent 4.5 billion years of Mars history, such as volcanic eruptions, a lot of clay deposits and asteroid and comet impact excavated others.

The modeling results are consistent with some probes and rovers are actually on the Red Planet, Cannon said.

“To a couple of tracks on, the clay coverage of about 3 percent of the oldest crust claims on Mars,” he said in the statement. “We found approximately the same order of magnitude in these models.”

Getting an answer

The new study, which was published today (Dec. 6) in the journal Nature, does not prove anything. But it makes a number of testable predictions that can help researchers learn more about the Red Planet’s ancient climate, study team members said.

For example, noble gases such as krypton and xenon were probably very common in the primordial outgassed atmosphere, Cannon told So many of these elements in the Martian clay would be the support of the steam-bath hypothesis advanced in the new study.

These measurements probably can’t be made of course, Cannon added: “They could be the work of an advanced rover on the site, or better yet, the analysis of the returned Martian samples in the well-equipped labs here on Earth.

NASA’s next Mars rover, which is due to start in 2020, will collect and store samples for possible transport to Earth. But that return is only conceptual at the moment; there is no mission on the space agency’s books to such samples for our planet.

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