NASA MER-A · Mission Complete (2004–2010)
The twin sister of Opportunity, Spirit landed in Gusev Crater on 4 January 2004 — three weeks before its sibling arrived at Meridiani Planum. While Spirit's landing site initially disappointed scientists with its lack of obvious water evidence, the rover's journey to the Columbia Hills revealed some of the mission's most important discoveries, including silica deposits proving past hydrothermal activity.
2,208 sols (6 years, 77 days). Designed for 90 sols. Exceeded design life by 24×.
7.73 km across the plains and into the Columbia Hills. The terrain was far rougher than Opportunity's flat plains.
Gusev Crater (14.57°S, 175.48°E). A 166 km-wide crater believed to have once held a lake fed by Ma'adim Vallis, one of the largest outflow channels on Mars.
185 kg. Same instrument suite as Opportunity: Pancam, Mini-TES, APXS, Mössbauer, MI and RAT. Solar-powered.
Silica-rich soil near Home Plate — nearly pure silica (90%+) that could only form in hot springs or volcanic steam vents, proving past hydrothermal activity.
Became stuck in soft soil at a site called Troy in May 2009. Operated as a stationary observatory until losing contact in March 2010 during its fourth Martian winter.
Gusev Crater was chosen because orbital data suggested it once held a lake. But the crater floor was covered in volcanic basalt — no obvious water signatures. Scientists directed Spirit toward the distant Columbia Hills, hoping older rocks there would tell a different story.
After a 3 km drive across the plains, Spirit reached the Columbia Hills in June 2004. The hills — named after the seven astronauts lost in the Columbia shuttle disaster — contained altered rocks with minerals formed only in the presence of water. Goethite, hematite and sulphate salts proved that water had percolated through these rocks.
At a volcanic formation called Home Plate, Spirit discovered soil with up to 90% silica. On Earth, such concentrations occur only around hot springs or volcanic fumaroles where acidic steam dissolves everything except silica. This was the strongest evidence yet for past hydrothermal environments on Mars — environments that on Earth teem with microbial life.