Radar sounding of the Medusae Fossae Formation Mars: equatorial ice or dry, low-density deposits? - Watters TR; Campbell B; Carter L; Leuschen CJ; Plaut JJ; Picardi G; Orosei R; Safaeinili A; Clifford SM; Farrell WM; Ivanov AB; Phillips RJ; et al. (Science (New York, N.Y.), 2007)