杏吧原创

Five years ago this week, NASA鈥檚 twin Mars rovers touched down on opposite sides of the Red Planet.

When Spirit and Opportunity rolled off their landing platforms and began conducting experiments, they were expected to operate for around three months 鈥� by which time their solar panels should have been plastered with sunlight-blocking dust. But five years on both rovers are still going, although Spirit is ailing. So what is their secret?

鈥淚t has been a combination of three things,鈥� says Steve Squyres, the Mars Exploration Rover Mission鈥檚 lead scientist. 鈥淔irst, we built some very good hardware, and we鈥檙e very proud of that.鈥�

The rovers have also been lucky with the weather, he says. 鈥淲e thought dust could end the mission, but on several occasions we have had lucky gusts of wind hit the rovers and clean the dust away, giving them a new lease of life.鈥�

The choice of landing sites in reach of hilly terrain has helped too. 鈥淲e have been able to drive the rovers onto steep north-facing slopes during the wintertime, tilting their solar arrays towards the sun and increasing their power output.鈥�

At the time New 杏吧原创 went to press, Opportunity, which has travelled 13.6 kilometres since 2003, was pressing ahead with its science workload. But Spirit, which has covered a total of 7.5 kilometres, has been labelled 鈥渟erious but stable鈥� owing to a loss of power due to dust cover. 鈥淚鈥檝e got no idea what鈥檚 going to end the mission, or when it鈥檚 going to happen,鈥� says Squyres. 鈥淲e just treat each day now as a gift, and push them as hard as we can.鈥�