Phobos And Deimos & Mars Environment Phobos And Deimos & Mars Environment Phobos And Deimos & Mars Environment (PADME) is a low-cost NASA Mars orbiter mission concept that would address longstanding unknowns about Mars' two moons Phobos and Deimos and their environment. The PADME mission competed for Discovery Program funding, but lost to the Psyche and Lucy missions. The mission is led by Anthony Colaprete (Principal Investigator). Other principals include Pascal Lee (Deputy Principal Investigator) and Butler Hine (Project Manager). The origin of Mars' satellites, which were discovered by astronomer Asaph Hall, remains unknown. PADME would advance the scientific understanding of the origin of Phobos and
Lithobraking launched, including penetrators on the two Phobos probe landers targeted for Mars' moon Phobos and ones for Mars itself on Mars 96 and Deep Space 2, but so far none have succeeded. The cancelled LUNAR-A probe would have carried penetrators to the Moon. Lithobraking as a method for de-orbiting a spacecraft has not been used due to the extremely high orbital velocities of most bodies (e.g. for the Moon it is over 7000 km/h). However, some small moons and asteroids have very low gravity and it could conceivably be used there (e.g. Phobos has an "escape velocity" of 40 km/h.)