Today marks the fifth anniversary of the day that Opportunity, one of NASA's Mars Exploration Rovers, landed on the ruddy Meridiani Plain. Its twin, Spirit, thumped down in Gusev Crater three weeks earlier. Both were designed for 90-day missions, yet remarkably both are still operating on the Martian surface.
I was tempted to say "both are still hard at work," but that wouldn't be truthful. Spirit is having a tough time these days. A series of dust storms that began in 2007 has covered its solar-cell panels with so much dust that less than 30% of the sunlight is getting through — and that sunlight is weakened further by dust still suspended in the atmosphere.
Spirit's darkest days came in November, when ground controllers reported that on average the panels were generating only 169 watt-hours of electricity, compared to the robust 900 available back in 2004. Experiments have been idled and heaters turned off as Spirit clings to electronic life.
But the skies are clearing, and mission engineers are hoping to power up the instruments soon. At least it's got a nice view, overlooking Gusev's expansive floor from a perch in the Columbia Hills. If and when Spirit gets to roam again, it'll do so with a broken front wheel that's been dragging along for years.
All told, Spirit has covered 4.68 miles (7.53 km) since its arrival.
Meanwhile, Opportunity continues to frolic. You'll recall that it landed in a small crater, where it discovered countless small spheres of the mineral hematite ("blueberries") that could only have formed in water. By contrast, Spirit struggled to find water's signature on the floor of Gusev. In fact, chief scientist Steve Squyres affectionately refers to Opportunity as "Little Miss Perfect" because it's performing so well.
"LMP" has been crater-hopping ever since landing in one. It reached a small crater named Endurance in mid-2004 and another called Erebus en route to the dramatic Victoria crater 4 miles (7 km) from the landing site. A half mile (800 meters) wide, Victoria proved so rich in geologic surprises that mission scientists kept Opportunity there for two years.
Now it's set off again on another audacious quest: to reach a much larger crater named Endeavour some 7 miles (12 km) to the southeast. It could take two years to reach, but Squyres recently told me that Opportunity has plenty of juice (500 to 600 watt-hours daily) and is zipping effortlessly across the terrain at brisk clip.
As of December 17, 2008, Opportunity had clocked 8.46 miles (13.62 km).
I saw Steve two weeks ago at Boston's Museum of Science for the debut of the Disney film Roving Mars in the museum's Omnimax theater. With him was director George Butler. The film has been around for three years, but its launch and animation sequences look utterly dramatic when viewed on that big screen.
I chuckled at the end, because the narrator (the late Paul Newman) notes that both rovers are still working hard — and the film was released three years ago!
To fully appreciate everything these roving Martian ambassadors have accomplished, I recommend you pick up a copy of Squyres' 2005 book Roving Mars: Spirit, Opportunity, and the Exploration of the Red Planet or Jim Bell's more recent Postcards From Mars.