Astronomy & Space Word of The Day
dark terrain: A type of surface on Ganymede and Callisto which is darker than other regions on these moons (see also bright terrain). On Ganymede dark terrain is often associated with furrows.
1964: Mariner 4 - USA Mars Flyby (November 28, 1964 - December 20, 1967) launched. Mariner 4 arrived at Mars on July 14, 1965 and passed within 9,920 kilometers of the planet's surface. It returned 22 close-up photos showing a cratered surface. The thin atmosphere was confirmed to be composed of carbon dioxide in the range of 5-10 mbar. A small intrinsic magnetic field was detected. Mariner 4 is now in a solar orbit.
1967: Mariner 5 - USA Venus Flyby (June 14 to November, 1967) completed its journey. Mariner 5 arrived at Venus on October 19, 1967, one day after Venera 4. It passed within 3,900 kilometers of the planet's surface. It studied the Venusian magnetic field and found that its atmosphere was composed of 85-99% carbon dioxide. It is now in a solar orbit.
1995: Pioneer 11 - USA Jupiter/Saturn Flyby - 259 kg - (April 6, 1973 - November 1995) left the solar system. Pioneer 11 flew by Jupiter on December 1, 1974 passing 42,900 kilometers from Jupiter's cloud tops. It took better pictures than Pioneer 10, and measured Jupiter's intense charged-particle and magnet field environment. As it flew by Jupiter it was given a gravity assist which swung it onto a course for Saturn. On September 1, 1979, Pioneer 11 flew past the outer edge of Saturn's A ring at a range of 3,500 kilometers. It traveled underneath the ring system and passed 20,930 kilometers from Saturn's cloud tops.