May 27, 2011 -- NASA's rover Spirit arrived at Mars on Jan. 4, 2004, to answer some questions about the role of water in the planet's past.
The mission, designed to last three months, was to analyze rocks and soil samples in Gusev Crater, believed to be a dry lakebed.
The landing site, however, turned out to be volcanic material as far as the rover eye could see, says project manager John Callas, with NASA's Jet Propulsion Laboratory in California. So the team dispatched Spirit across the plains in an attempt to reach the distant Columbia Hills, named after the astronauts killed in the 2003 shuttle accident.
Hundreds of images were combined for this view from the top of Husband Hill, named for Columbia commander Rick Husband.
Mission on Mars
Spirit was a field geologist, tasked with finding interesting rocks and unusual patches of soil. Its toolkit included a wire brush to scour a rock’s surface, a small grinder to bore down into its interior and an alpha particle X-ray spectrometer to chemical identify minerals.
It was on the Columbia Hills that Spirit found its first evidence of water-altered rocks, and later carbonates, says Callas.
Places I've Been
NASA never expected the rover to drive more than about a half-mile from where it touched down on Mars, but it ended up putting almost 5 miles on its odometer.
After nearly a year on Mars, the rover took these shots showing its tracks across the dusty Martian surface.
Tooling around on Mars was no picnic.
The rover lost use of its right front wheel while climbing down Columbia Hills. And then there was the dust. Massive accumulations greatly impacted the amount of solar energy the rover could harvest.
In this 2007 image, the rover’s solar panels are barely distinguishable from the dusty background. "Spirit had an ever-increasing accumulation of dust on her arrays. Each winter became harder than the last," writes Callas in a letter to his team.
Spirit had a secret weapon to discern interesting dust-covered rocks from ordinary ones on Mars: a miniature thermal emission spectrometer, which is a kind of infrared divining rod for ferreting out the composition of materials from afar.
One of the rover’s first finds was this phosphorus-rich rock nicknamed "Wishstone." The round hole in the middle of the rock is where Spirit neatly brushed away its dust covering for a close-up inspection. Three images were combined in this color-enhanced picture.
One of Spirit’s most important discoveries was this patch of unusually light soil, which turned out to be nearly pure silica -- the primary ingredients in quartz and glass. On Earth, silica usually is formed by volcanic steams or hot springs, both tantalizing hints of a water-rich past on Mars.
The soil was unearthed in 2007 by Spirit’s broken and dragging front wheel.
Living on Mars is not without surprises.
Here a windstorm known as a dust devil blasts past Spirit’s navigation camera. Dust devils turned out to be a very common occurrence on the floor of Gusev Crater. Martian dust devils can be 50 times wider and 10 times taller than terrestrial ones.
In March 2005, a fortuitously positioned dust devil is believed to cleaned off Spirit’s solar panels by blowing away accumulated dust.
Sunset on Mars
May 19, 2005, may have started off like any other day on Mars, but it ended on a poignant note, with this view of the sun sinking below the rim of Gusev Crater.
The twilights last a long time on Mars, as high-altitude dust causes sunlight to scatter around to the dark side of the planet.
The beginning of the end for Spirit came two years ago when the rover became stuck in soft sand. In April 2009, Spirit used its hazard-avoidance camera for this wide-angle view of the problem.
Control teams on Earth tried for months to extricate the rover, which ended up losing use of a second wheel in the process. It still did science, however, as a stationary lander.
Unable to drive itself to a sunnier winter roost where it could power its heaters, Spirit likely succumbed to the frigid Martian cold.
Here's a panoramic view from where it sits, a composite of hundreds of images taken between May 14 and June 20, 2009. North is at center, south at either end. The western edge of a plateau called "Home Plate" dominates the right half panorama.
At far right is a bright mound called "Von Braun." That will be for future explorers to discover.
NASA this week gave up trying to contact the rover. "She died an honorable death," lead scientist Steve Squyres writes in an email to Discovery News. "We've learned that early Mars at Spirit's site was a hot, violent place, with hot springs, steam vents and volcanic explosions. It was extraordinarily different from the Mars of today."
"She accomplished so much more than any of us expected," he adds. "The sadness is very much tempered with satisfaction and pride."