Scientists are hitting pay dirt on Mars

Kenneth ChangThe New York Times
NASA

It looked to be uniformly bland, which is why scientists chose it as the first rock to be examined up close last year by the Mars rover Curiosity: a run-of-the-mill volcanic rock, something to test and calibrate the rover's instruments.

The rock turned out to be anything but ordinary, scientists reported last week. It is unlike any Mars rock previously examined and more like an Earth rock.

And as for the pile of windblown dust and soil that the rover spent weeks analyzing? It was not dry as dust, but contained water.

Such are the surprises that turn out to be a near constant of Mars exploration, according to six new papers on the red planet that appeared last week - five in the journal Science and one in The Journal of Geophysical Research: Planets.

The new findings are "the nuts and bolts" of what Curiosity has discovered so far, said John P. Grotzinger, the mission's project scientist. On Sept. 19, another paper from the science team reported that Curiosity had not detected any methane, which could have been a sign of present-day microbes. The mission is designed to see whether the building blocks of life existed on Mars, especially in the distant past, but includes no experiments to directly detect life.

In September last year, Curiosity rolled up to the volcanic rock, a pyramid-shaped chunk about the size of a football. The science team named it Jake M., after Jacob R. Matijevic, a longtime NASA rover engineer who had died the month before.

It appeared to be a chunk of basalt, like many others strewed on the Martian surface.

"Just featureless," said Edward M. Stolper, a professor of geology at the California Institute of Technology and the lead author of one of the Science papers. "It wasn't expected to be interesting."

Then the first readings came back. The mix of elements was different from that of other Martian basalts. "It just didn't look like any of the other guys," Stolper said. "I could tell that this was an unusual rock type and that it had characteristics that reminded me of certain kinds of terrestrial rocks."

The rock was alkaline, similar to a well-known but uncommon type of rock called mugearite, which is found on volcanic islands like Hawaii. "People say that less than 1 percent of the rocks on Earth are alkaline," Stolper said. "If you plopped down on Earth, you wouldn't find something like this likely randomly."

On Earth, the magma that hardens into alkaline rocks comes from the melting of rocks deep in the mantle in the presence of water. That suggests that the movement of magma and other geological processes within Mars may have been more complex and interesting than has been thought.

"People say, 'Sure, why not?' but we haven't seen it before," Stolper said of the composition of Jake M. "It's not a little bit different. It's a lot different."

In October, Curiosity visited the dirt pile - a stationary Martian dune piled up by gale-force winds 50,000 to 200,000 years old - and performed the first soil test in its chemistry laboratory, which is packed into a space the size of a microwave oven. The fine dust in the pile, which was named Rocknest, was expected to be a mix of what is blowing around the entire planet.

"It looks pretty similar everywhere we go," said Laurie A. Leshin, a professor of earth and environmental science at Rensselaer Polytechnic Institute and the lead author of another of the Science papers.

When the dirt was scooped into the lab and heated, it released water vapor. Other analysis showed that the dirt and dust consisted of both tiny crystals where the atoms lined up in neat patterns and what the scientists called "amorphous" materials - the atoms jumbled up randomly, as in glass.

There was no evidence of water in the crystallized minerals, so all of the water - 2 percent by weight - was chemically bound up in the glassy particles.

"It's actually a fair amount," Leshin said. "We always think of Mars as being this dry desert planet."

The water in the dust could be a resource for future astronauts. Heating up a cubic foot of dirt would yield a couple of pints of water, Leshin said.

Grotzinger, the project scientist, said the water could also conceivably be something for hypothetical Martian microbes to drink, although Curiosity has yet to find any of the molecules necessary for carbon-based life.

Possibly complicating life for human visitors, Curiosity also found that the chemicals called perchlorates, which can cause thyroid problems, are prevalent at the landing site. An earlier NASA mission, Phoenix Mars, had found perchlorates near the north pole.

"It's suggesting perhaps a global distribution of these salts," said Daniel P. Glavin, an astrobiologist at NASA's Ames Research Laboratory and the lead author of the paper that reported the perchlorate findings.

The perchlorates also complicate Curiosity's search for the carbon-based molecules known as organics that could be the building blocks for life, past or present. Heated in the presence of perchlorates, organic molecules disintegrate into simple carbon dioxide.


By KENNETH CHANG
The New York Times