on board. The robotic arm is able to place instruments directly up against rock and soil targets of interest. Naming of Spirit and Opportunity The Spirit and Opportunity rovers were named through a student essay competition. The winning entry was by Sofi Collis, a third-grade Russian-American student from Arizona. I used to live in an orphanage. It was dark and cold and lonely. At night, I looked up at the sparkly sky and felt better. I dreamed I could fly there. In America, I can make all my dreams come true. Thank you for the 'Spirit' and the 'Opportunity.' — Sofi Collis, age 9 Prior to this, during the development and building of the rovers, they were known as MER-1 Rover 1 (Opportunity) and MER-2 Rover 2 (Spirit). Internally, NASA also uses the mission designations MER-A (Spirit) and MER-B (Opportunity) based on the order of landing on Mars. Test rovers The Jet Propulsion Laboratory maintains a pair of rovers, the Surface System Test-Beds (SSTB) at its location in Pasadena for testing and modeling of situations on Mars. One test rover, SSTB1, weighing approximately , is fully instrumented and nearly identical to Spirit and Opportunity. Another test version, SSTB-Lite, is identical in size and drive characteristics but does not include all instruments. It weighs , much closer to the weight of Spirit and Opportunity in the reduced gravity of Mars. These rovers were used in 2009 for a simulation of the incident in which Spirit became trapped in soft soil. SAPP software for image viewing The NASA team uses a software application called "Surface Attitude Position and Pointing" (SAPP), to view images collected from the rover, and to plan its daily activities. There is a version available to the public called Maestro. Planetary science findings Spirit Landing Site, Gusev Crater Plains Although the Gusev crater appears from orbital images to be a dry lakebed, the observations from the surface show the interior plains mostly filled with debris. The rocks on the plains of Gusev are a type of basalt. They contain the minerals olivine, pyroxene, plagioclase, and magnetite, and they look like volcanic basalt as they are fine-grained with irregular holes (geologists would say they have vesicles and vugs). Much of the soil on the plains came from the breakdown of the local rocks. Fairly high levels of nickel were found in some soils; probably from meteorites. Analysis shows that the