PADME (Phobos And Deimos & Mars Environment): A Proposed NASA Discovery Mission

Ever the since their discovery in 1877 by American astronomer Asaph Hall, the two moons of Mars, Phobos and Deimos, have been enigmas. Spacecraft missions have revealed irregular-shaped small bodies with different densities, morphologies, and evolutionary histories. Spectral data suggest that they might be akin to D-type asteroids, although compositional interpretations of the spectra are ambiguous. The origin of Phobos and Deimos remains unknown. There are three prevailing hypotheses for their origin: 1) They are captured asteroids, possibly primitive D-type bodies from the outer main belt or beyond; 2) They are reaccreted impact ejecta from Mars; 3) They are remnants of Mars’s formation. Each one of these hypotheses has radically different and important implications regarding the evolution of the solar system, and/or the formation and evolution of planets and satellites, including the delivery of water and organics to the inner solar system. The Phobos And Deimos & Mars Environment (PADME) mission is a proposed NASA Discovery mission that will test these hypotheses, by investigating simultaneously the internal structure of Phobos and Deimos, and the composition and dynamics of their surface and near-surface materials. PADME would launch in 2020 and reach Mars orbit in early 2021. PADME would then begin a series of slow and increasingly close flybys of Phobos first, then of Deimos. PADME would use the proven LADEE spacecraft and mature instrument systems to enable a low-cost and low risk approach to carrying out its investigation. In addition to achieving its scientific objectives, PADME would fill strategic knowledge gaps identified by NASA’s SBAG and HEOMD for planning future, more ambitious robotic landed or sample return missions to Phobos and/or Deimos, and eventual human missions to Mars Orbit. PADME would be built, managed, and operated by NASA Ames Research Center. Partners include the SETI Institute, NASA JPL, NASA GSFC, NASA JSC, NASA KSC, LASP, Cornell U., U. of Central Florida, U. of Maryland, U. of Virginia, Lowell Observatory, Royal Observatory of Belgium, Observatoire de la Cote d’Azur, and JAXA.