Robots on Mars!

The mood at the news conference was sombre. For nine months, the Mars Exploration Rover known as Spirit had been stuck in a sand pit on the rim of a shallow crater. The mission team had tried its best to free the robot, a NASA official told reporters, but now it was time to face reality: her current location would likely be her “final resting place”. After six years of roaming the Red Planet, the intrepid explorer was being redesignated a “stationary research platform”.

The very next day – January 27, 2010 – Spirit began edging, centimetre by centimetre, towards solid ground. Reports of the rover’s death, quipped the mission’s lead scientist, Steve Squyres, were “greatly exaggerated”.

Spirit and her identical twin, Opportunity, have been defying the odds ever since they landed on Mars in January 2004. When they first rolled off across the rust-coloured landscape at a leisurely 60cm per minute, the hope was they would make it through their three-month mission.

This spring, they were on track to break the endurance record held by the stationary probe Viking I, which stopped communicating with Earth in 1982 after six years and 116 days. The golf-cart-size rovers have travelled more than 27km, beamed back some 260,000 images and inspected at great length hundreds of rocks and patches of soil. In the process, they have given us our most intimate view yet of the desolate planet and provided conclusive evidence that water once flowed there.

Surviving on Mars is not easy. Temperatures can vary by 55C in the space of a single day, stressing delicate machine parts. Weeks-long dust storms coat instruments and solar panels with powder stirred up from the planet’s surface. Solid-looking terrain sometimes crumbles, trapping wheels in the sand beneath. Yet Spirit and Opportunity continue to clamber over hurdles, rebound from setbacks and double cross death. Around the world, millions of fans have followed the unfolding drama on the internet.

Of course, Spirit and Opportunity are made of steel, aluminium and composite materials, and are incapable of expressing traits such as courage and persistence. So it may be surprising to learn that even scientists and engineers who work with the rovers often speak of them in human terms. “Some of us have really fallen in love with these girls,” says Sharon Laubach, who until recently led the crew that commands the rovers. In fact, some team members describe the machines as having two distinct – and not always harmonious – personalities.