The age-old question of whether or not there is life on Mars has prompted many missions to this mysterious planet, and this manual covers the development, design and engineering of three generations of Mars rovers. Sojourner was the first to land in 1997 and was the size of a microwave, Spirit and Opportunity followed in 2004 and were both the size of a shopping trolley, and Curiosity landed most recently in 2012 and is the size of a car, with a design life of two years.