In 1997, the Mars Pathfinder, an unmanned space vehicle, reached the Martian atmosphere. It had taken seven months to travel there since its launch on 4 Dec 1996. Its main science mission was to study the Martian atmosphere and investigate the geology and chemical composition of the planet’s rocks and soils. The descent was braked by a heat shield, a parachute and rockets. Using a new NASA effort for “cheaper, faster, better,” the Mars Pathfinder used airbags to cushion its landing on the surface. It carried Sojourner, a 10 kg (22 lb) wheeled rover device designed to travel slowly across the surface of Mars taking photographs and collect other scientific data, while also testing autonomous-vehicle technology on the Martian terrain.