Exploration of Mars failed upon impact. Mars 4 flew by the planet at a range of 2200 km returning one swath of pictures and radio occultation data, which constituted the first detection of the nightside ionosphere on Mars. Mars 7 probe separated prematurely from the carrying vehicle due to a problem in the operation of one of the onboard systems (attitude control or retro-rockets) and missed the planet by . In 1964, NASA's Jet Propulsion Laboratory made two attempts at reaching Mars. Mariner 3 and Mariner 4 were identical spacecraft designed to carry out the first flybys of Mars. Mariner 3 was launched
Space-based radar and, thus, the unwanted echo from other surface objects. The first radar sounder flown was ALSE (Apollo Lunar Sounder Experiment) on board Apollo 17 in 1972. Other sounder instruments flown (in this case around Mars), are MARSIS (Mars Advanced Radar for SubSurface and Ionosphere Sounding) on board the European Space Agency's Mars Express probe, and SHARAD (mars SHAllow RADar sounder) on JPL's Mars Reconnaissance Orbiter (MRO). Both are currently operational. A radar sounder is also used on the Japanese Moon probe SELENE, launched September 14, 2007. A similar instrument (primarily devoted to ionospheric plasma probing) was embarked on the Japanese