Editorial: “Curiosity: A Mars robot for our times“
“Touchdown confirmed!” said landing engineer Allen Chen at 10.32 pm Pacific Standard Time on 5 August. “We’re safely on Mars.” Scientists and engineers hugged and punched the air as confirmation of the Curiosity rover’s landing reached Earth.
It was a “miracle of engineering”, says project scientist John Grotzinger at . “Everything went so smoothly, I had to keep reminding myself it wasn’t a test run.”
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Having nailed its death-defying landing, the 1-tonne Curiosity is ready to begin the main phase of its mission on the Martian surface, due to last for a minimum of two years: to find out whether the Red Planet had the crucial ingredients that could once have supported life.
The rover touched down about 2 kilometres east of the centre of the ellipse that flight engineers were aiming for, in the north-west quadrant of .
Its eventual destination is Aeolis Mons – also known as Mount Sharp – a 5-kilometre-high mountain in the crater’s centre. As Curiosity climbs the peak’s lower slopes, it should encounter layers of sediments described by mission manager Mike Watkins as a “treasure trove”.
Deep time
Gale formed as an impact crater, but its geology suggests that it was full of water for hundreds of millions of years. This means that the sediments on Aeolis Mons should contain a complete record of this history, revealing what Grotzinger calls “the dimension of deep time” on Mars.
The rover landed with its front wheels facing south and its forward hazard camera looking right towards the mountain, about 6.5 kilometres away. “This couldn’t have been a better position to land,” says Grotzinger.
Despite the lure of Aeolis Mons, mission scientists are in no hurry to rush away from the landing site. “This is our new home, at least for a while,” says Watkins. “We need to explore it and take a look around – and of course eventually head for the hills.”
For one thing, a lengthy testing process lies ahead as the team makes sure all the instruments are working properly. But there is also plenty of science to be done in the vicinity. “What we’ve got here is a geologist’s paradise,” says Grotzinger.
Water mystery
Curiosity has landed at or near the end of a feature called an alluvial fan, which forms when a stream of water flows onto a flat plain, slowing down and spreading out. This should mean that material from far away – possibly from the crater wall, 28 kilometres away – is sitting nearby. “We get to double dip,” says Grotzinger. “We’re getting a free sample without having to drive over there, potentially.”
Comparing the fan with Aeolis Mons could help answer one of the biggest questions about Mars: when did the planet lose its water? Viewed from orbit, there seems to be a discontinuity on the mountain – a sudden change in rock colour – thought to represent the “Great Desiccation Event”, when Mars went from a wet to a dry world some 3 billion years ago.
But if the material in the fan turns out to be younger than the sediments on the mountain and the crater floor, it would change that simple story. “Maybe there were times when it got wet again,” Grotzinger says.
The ground beneath Curiosity seems to be compacted, so the rover will have to move before taking its first scoops of soil. When it does, mission scientists expect the rover to pick up dust that may have blown in from all over the planet, representing “average” surface conditions on Mars. It should be similar to that sampled by other landers, including the two Viking craft in 1976.
… and stretch
In the next few days, the rover will stretch its robotic “arm” and “neck”. The former carries a suite of instruments including a camera that will be used to peer at rocks, like a geologist using a hand lens. The latter is a mast carrying high-resolution cameras that will reveal panoramas of Curiosity’s surroundings, and a laser that will zap rocks from up to 7 metres away to help reveal their composition.
The laser, part of the , will probably fire up by the tenth Martian day of the mission (Martian days last about 40 minutes longer than Earth’s). Once the rover gets rolling, it will probably sample rocks at least once a day, to see what they’re made of and if they’re worth driving up to for a closer look.
The , a massive on-board chemistry lab, will probably take the first “sniff” of the Martian atmosphere within a few weeks. When it gets into its scientific stride, Curiosity will use this lab and other instruments to look for the organic molecules that make up the building blocks of life, and chemicals that could have been energy sources for Martian microbes.
Crowdsourced route
Even from the first sniff, SAM could help solve the mystery of Martian methane. Observations from orbit suggest that Mars is oozing distinct plumes of the short-lived gas. This could mean either the planet is geologically active, or something is or was alive there that could eat or produce methane.
Curiosity’s itinerary is still being worked out. To get to Aeolis Mons it will have to find a safe way to traverse a dark field of dunes, which are slow and dangerous to drive through.
The rover’s path will also be planned according to scientific priorities. Before landing, Grotzinger split the landing ellipse into a grid of about 50 1-kilometre squares. In a crowdsourced mapping effort, he got volunteers from the science team to survey those squares in detail.
This has shown that the landing ellipse is littered with scarps – blocks of bedrock, 1 or 2 metres high, that could host layered sediments of their own. One path the rover could take to Aeolis Mons is to string interesting scarps together like pearls, Grotzinger says. “If it takes a year to get there, that’s OK.”
