Mosaic image of the robotic Sojourner rover aboard the Mars Pathfinder on the surface of the "red planet". Sojourner has an Alpha-Proton X-Ray Spectrometer (APXS) and a high-resolution camera to study rocks. The rover weighs about 9 kilograms, is 63 centimeters long and 48cm wide. It is powered by a solar panel which will allow for a few hours movement per day. An operator on Earth chooses Sojourner's next destination, but the vehicle itself calculates the best route to take. Image taken by the Imager for Mars Pathfinder (IMP) on the day that it landed (Sol 1) on 4 July 1997.