Of all Mars spacecraft, only a third has succeeded in completing their mission.
Turns out that sending things to Mars is pretty hard, go figure.
As part of the Mars Exploration program, NASA had sent the following landers to Mars: Viking 1, Viking 2 and the Mars Pathfinder.
The next Mars-bound launch in that series were two rovers of the Mars Exploration Rovers mission (MER).
The Spirit and Opportunity rover were launched in 2003. The Spirit rover (MER-A) arrived on Mars on January 3rd 2004 and the Opportunity rover (MER-B) 22 days later, on 25 January 2004.
Launch of MER-A (left), and MER-B (right)
Mars Exploration Rover Mission Objective
As early as the Mariner 9 mission, NASA had been exploring the Red Planet.
The objective of the Mars Exploration Rover mission was to explore Martian surface and geology.
More specifically investigate rock and soil that might give more information about water on Mars.
The mission was supposed to last 90 solar days, or sols (about 92 Earth day).
But both rovers have far outlived that initial plan.
Spirit Rover
The Spirit rover landed in the Gusev crater.
Mars Sunset Poster By Spirit rover
The Sun setting at Mars on 19 May 2005 as captured by NASA’s Mars Exploration Rover Spirit.
The Spirit rover got stuck in soft soil in May of 2009 during its 5th mission extension. After it assumed the task of being a stationary science platform. In 2010 all communication was lost.
Opportunity Rover
The Opportunity rover landed at the Sinus Meridiani region, about half the planet away from its twin.
The rover is still active today (4974 sols into the mission) and holds the record of largest distance by a vehicle on a planet other than Earth: 42 km (26.2 miles) in 2015.
NASA Opportunity rover in the clean room before launch.
Sometimes a dust storm covers its solar panels, causing the rover to go into hibernation. But the next storm might clears the dust, allowing the Opportunity rover to restart its mission.
Scientific findings
The most significant findings have been evidence that liquid water has existed in the past at both landing sites.
Explore our collection of Mars posters.