Mars Pathfinder was designed to be a demonstration of the technology necessary to deliver a lander and a free-ranging robotic rover to the surface of Mars. Pathfinder not only accomplished this goal but also returned an unprecedented amount of data and outlived its primary design life. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight wheeled robotic rover named Sojourner. Launched in December 1996 aboard a Delta II booster it landed on July 4, 1997 on Mars. The mission carried a series of scientific instruments to analyze the Martian atmosphere, climate, geology and the composition of its rocks and soil.
NASA's twin robot geologists, the Mars Exploration Rovers, were robotic space probes named Spirit and Opportunity. The two rovers were launched in 2003, MER-A Spirit and MER-B Opportunity. After the airbag-protected landing craft settled onto the surface and opened, the rovers rolled out to take panoramic images. The images returned gave scientists the information they needed to select further locations for soil testing. On May 1, 2009, during its fifth mission extension, Spirit became stuck in soft soil on Mars. After nearly nine months of attempts to get the rover back on track NASA announced on January 26, 2010 that Spirit was being re-tasked as a stationary science platform. Contact with Spirit was lost on March 22, 2010.
The Curiosity rover is about five times larger than the Spirit or Opportunity Mars Exploration Rovers and carries more than ten times the mass of scientific instruments. It was launched by an Atlas V 541 rocket in November 2011 and is scheduled to reach Mars on August 6, 2012. It is designed to explore the surface of Mars for at least 687 Earth days (1 Martian year). One mission objective is to determine whether Mars is or has ever been able to support life. This can be accomplished by the rovers various abilities: chemically analyzing samples in various ways, scooping up soil, drilling rocks, using a laser for analysis and various other sensor systems.
An unprotected human can survive up to 1.5 minutes in space with no permanent bodily damage.