Sojourner. View of the Mars Pathfinder robotic rover vehicle Sojourner" during assembly. This rover vehicle landed on Mars on 4 July 1997. It weighs about 9 kilogrammes, is 63 centimetres (cm) long and 48cm wide. It's wheels and suspension are designed for movement over Mars' rocky surface. It is powered by a solar panel (at top) which allows for a few hours of movement per day, and is controlled by an operator on Earth. The Sojourner is equipped with an Alpha Proton X-Ray Spectro- meter (APXS). The APXS determines the chemical composition of martian rocks. All elements except hydrogen can be detected during the ten hours the APXS takes to complete an analysis."