 A proposed landing site for the PRIME spacecraft is at the "Phobos monolith", a prominent object near Stickney crater.The PRIME mission would be composed of an orbiter and lander, and each would carry 4 instruments designed to study various aspects of Phobos's geology.In 2008, NASA Glenn Research Center began studying a Phobos and Deimos sample return mission that would use solar electric propulsion.