The US space agency's Opportunity rover has rewritten a 41-year-old driving record that is out of this world. The decade-old Nasa Mars rover has crossed the 40km mark, surpassing the 39km record held by the Russian moon rover Lunokhod 2.
Not too shabby for a rover that landed on the red planet in 2004 with a 90-day mission and an odometer geared for a roughly 0.96km drive, said John Callas, the mission's project manager at Nasa's Jet Propulsion Laboratory in La Canada Flintridge, California.
"No one in their wildest dreams thought the rover would last this long," Callas said. "People made bets early on - 'Maybe we can get to the first Martian winter', 'Maybe we can get two years out of it' - but no one thought that it would last this long."
No one's betting against Opportunity now. It may be ageing, with an arthritic elbow and a somewhat disabled front wheel, but it has long outlived its twin rover, Spirit, and lasted roughly 40 times as long as it was supposed to.
The previous record holder for distance, the Lunokhod 2, was sent loping around the moon's surface by Russia in 1973. It covered 39km in less than five months - speedy compared with Opportunity's 10-plus years.
Opportunity's extra distance has allowed its handlers to make remarkable discoveries, because the robotic explorer has been able to venture far outside its landing site.
Though it discovered hints of past water soon after landing in Eagle Crater, the water was acidic and unsuitable for life. Only after leaving its landing site and arriving at Endeavour Crater did the rover discover signs of neutral, drinkable water - a key ingredient for life-friendly environments.
If Opportunity can do about two more kilometres, it will reach Marathon Valley. The valley holds layers of rock rich in clay that could give new insight into the red planet's geological story. In that way, it is a little like Mount Sharp, the 4.8km-high mound in the middle of Gale Crater targeted by Nasa's bigger, more advanced Mars rover, Curiosity, which landed in 2012.
But in some ways, Callas said, Opportunity's target was even better.
Mount Sharp will give Curiosity a window on Mars as it was about 3.5 billion years ago. But Marathon Valley's layers could show Opportunity what Mars looked like about 4 billion, even up to 4.5 billion, years ago.
"The geology is older and more significant in terms of establishing the early habitability of Mars," Callas said. The clays could come from very early days, he said, a time when Mars could have been warm and wet - with similar conditions to early earth when life here first began to emerge.