New Scientist visits Death Valley to find out how human geologists read Earth's past in its present – and how the rover Curiosity will apply those tricks on Mars
I GAVE up trying to pretend I was a Mars rover half an hour into my mad scramble up a scree-covered mountain. NASA's gigantic Curiosity rover, due to land on the Red Planet in August, will never have to deal with slopes this steep, I grumble to myself. Or a sun this hot. Or sore legs. It doesn't sweat, and it will have a plutonium battery. Lucky robot.
Perhaps what I lack in plutonium I make up for in excitement. I am scaling this slope with a group of scientists and journalists led by John Grotzinger, project scientist for the Mars Science Laboratory (MSL), which launched Curiosity in November. The goal of this $2.5 million machine, the most ambitious ever sent to Mars, is geological: to analyse sediments that could have preserved organic compounds or other evidence of ancient microbes, if these were ever there. Here in Death Valley, armed with hammers and lenses, we are learning how geologists read Earth's past in its present - and how Curiosity will apply those tricks to Mars.
Curiosity will land wheels-first in a basin called Gale crater that scientists believe once contained a liquid of some kind. "Could've been water. Could've been beer," says MSL's Ken Edgett. The liquid trapped dust and sediment as it fell out of the sky, leading to the formation of a 5-kilometre-high mound in the basin's centre. Luckily for Curiosity, the mound presents the crater's history in a neat timeline from bottom to top. To read it, all the rover has to do is climb.
Death Valley has its own layered history. Though it is hard to imagine now, the parched peaks we are clambering over were once flat sea floor. Similar to Gale, sediments filtered through the seawater to settle on the bottom, gradually laying down these rocks. Plate tectonics then lifted the rocks and tilted them into a crazy jumble.
None of this is obvious to me as I start swinging my rock hammer, and bring rock chunks into focus with my hand lens. But Grotzinger, whose intuition has been sharpened by decades of fieldwork, casually reads the mountain's history in subtle variations of shade and texture that I can barely see. This is the sort of detective work geologists on Earth will have to do on images beamed back by Curiosity. A hand lens is "the one thing geologists don't leave home without", Grotzinger explains - and Curiosity carries one too, in the form of the camera MAHLI, or Mars hand lens imager.
To verify the source of the sediments I am holding, I would need to take them to a lab for chemical analysis. Bringing samples back to Earth isn't an option for Curiosity, so it will simply throw them into its in-built geochemistry lab.
Despite this, it won't be as fast as a human geologist. "What we just did," Grotzinger says after about an hour, "will probably take the rover a month. No kidding."
The mission will last two Earth years. That may seem a long time, but the uncertainty of the future of Mars exploration makes me want to slow the clock. After MSL, a big question mark hangs over NASA's future on Mars. The natural next step would be to bring samples back to Earth but with its current budget, NASA probably won't get around to that for at least a decade. In February, the agency slashed its ambitious plans to explore the Red Planet.
Private industry could pick up the slack. In a first for a commercial firm, SpaceX of Hawthorne, California, is planning to dock with the International Space Station. It's the first step in broader plans for private space firms to explore deep space, including Mars (see main story). "I think it makes total sense from an evolutionary point of view to have private companies do things that NASA pioneered," says Ashwin Vasavada of NASA's Jet Propulsion Lab in Pasadena, California.
For now, though, it is the NASA team that has seen more Mars rocks than anyone - hopefully enough to read the stories in the stones. "In geology," says Grotzinger's graduate student Katie Stack, "whoever sees the most rocks wins."