Six Wheels on Soil

Boots on the ground would be ideal if you’re a Mars geologist, but a roving robot is the next best thing. Curiosity is the latest and greatest of four rovers NASA has sent to explore Mars. All have had six wheels and a suspension system that lets them roll over large obstacles. Their overarching question: whether Mars ever had life.

Click rovers to see details

SOJOURNER
SPIRIT and OPPORTUNITY
CURIOSITY

SOJOURNER

Built and launched for only $150 million—a fraction of the cost of the stationary Viking landers of the 1970s—Sojourner was an overwhelmingly successful first test of Mars rover technology. Powered by a small solar panel, it returned 550 images, more than 15 chemical analyses of mineral samples, and extensive weather readings from the red planet’s surface.

Weight: 23.15 pounds (10.5 kilos)

Height: .91 feet (.28 m)

Max Speed: .387 inches/second (.022 mph/.0354 kmh)

Range: 40 feet (12.2 m)

Lifespan: July 4, 1997 - September 27, 1997

SPIRIT and OPPORTUNITY

The twin Mars exploration rovers Spirit and Opportunity were solar-powered, like Sojourner, but carried more sophisticated instruments. Landing on opposite sides of the planet, they each confirmed what images made by orbiting spacecraft had suggested: Large quantities of water once flowed on Mars. Opportunity still operates at the Endeavour crater.

Weight: 407.855 pounds (185 kilos)

Height: 4.9 feet (1.5 m)

Max Speed: 2 inches/second (0.112 mph/0.18 kmh)

Range: Spirit: 4.8 miles (7.7 km);
Opportunity: 22.13 miles (35.61 km) and counting

Lifespan: Spirit: January 4, 2004 - March 22, 2010;
Opportunity: January 25, 2004 - present

CURIOSITY

The size of a small car, Curiosity is powered by a generator containing plutonium. It has 17 cameras and a seven-foot arm that can drill into rocks and extract samples, which it then analyzes. Its first big result came in March: Mars had all the chemicals needed to support life.

Weight: 1,982 pounds (899 kilos)

Height: 7.2 feet (2.2 m)

Max Speed: 1.5 inches/second (0.0852 mph/0.137 kmh)

Range: Estimated at up to 12 miles (19 km)

Lifespan: August 6, 2012 - present

(Nominal mission is one Mars year, about 687 Earth days.)