Magnetosphere of Jupiter By 1973 the magnetic moment was known within a factor of two, whereas the tilt was correctly estimated at about 10°. The modulation of Jupiter's DAM by Io (the so-called Io-DAM) was discovered in 1964, and allowed Jupiter's rotation period to be precisely determined. The definitive discovery of the Jovian magnetic field occurred in December 1973, when the Pioneer 10 spacecraft flew near the planet. As of 2009 a total of eight spacecraft have flown around Jupiter and all have contributed to the present knowledge of the Jovian magnetosphere. The first space probe to reach Jupiter was Pioneer 10 in
Space probe on another planet (Venus) and to transmit data from there back to Earth. Upon its arrival at Mars on November 13, 1971, Mariner 9 became the first space probe to maintain orbit around another planet. First soft landing on Mars (December 2, 1971) The lander began transmitting to the Mars 3 orbiter 90 seconds after landing. After 20 seconds, transmission stopped for unknown reasons. First successful rover on Mars. The Mars Exploration Rovers, "Spirit" and "Opportunity" landed on Mars to explore the Martian surface and geology, and searched for clues to past water activity on Mars. They were each launched