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TABLE 15.2

Spacecraft missions to Venus
Date Name Owner Remark
Feb 12, 1961 Venera 1 U.S.S.R. Flyby
Aug 27, 1962 Mariner 2 U.S. Flyby
Apr 2, 1964 Zond 1 U.S.S.R. Flyby
Nov 12, 1965 Venera 2 U.S.S.R. Flyby
Nov 16, 1965 Venera 3 U.S.S.R. Crashed on Venus
Jun 12, 1967 Venera 4 U.S.S.R. Impacted Venus
Jun 14, 1967 Mariner 5 U.S. Flyby
Jan 5, 1969 Venera 5 U.S.S.R. Impacted Venus
Jan 10, 1969 Venera 6 U.S.S.R. Impacted Venus
Aug 17, 1970 Venera 7 U.S.S.R. Venus landing
Mar 27, 1972 Venera 8 U.S.S.R. Venus landing
Nov 3, 1973 Mariner 10 U.S. Venus, Mercury
flyby photos
Jun 8, 1975 Venera 9 U.S.S.R. Lander/orbiter
Jun 14, 1975 Venera 10 U.S.S.R. Lander/orbiter
May 20, 1978 Pioneer 12 U.S. Orbital
(also called studies of FIGURE 15.5 This is an image of an 8 km (5 mi) high volcano
Pioneer Venus 1 Venus on the surface of Venus. The image was created by a computer
or Pioneer Venus) using Magellan radar data, simulating a viewpoint elevation of
Aug 8, 1978 Pioneer 13 U.S. Orbital 1.7 kilometers (1 mi) above the surface. The lava flows extend
(also called studies of for hundreds of kilometers across the fractured plains shown in
Pioneer Venus 2 Venus the foreground. The simulated colors are based on color images
or Pioneer recorded by the Soviet Venera 13 and 14 spacecraft.
Venus)
Sep 9, 1978 Venera 11 U.S.S.R. Lander; sent
photos slowest of all the planets, and it does not have a magnetic field
even if some of the interior of Venus is still liquid as on Earth.
Sep 14, 1978 Venera 12 U.S.S.R. Lander; sent
photos The European Space Agency’s (ESA’s) orbiting Venus Ex-
press is conducting an in-depth observation of the structure and
Oct 30, 1981 Venera 13 U.S.S.R. Lander; sent
photos chemistry of the atmosphere of Venus. One of the early findings
Nov 4, 1981 Venera 14 U.S.S.R. Lander; sent was hot, extensive, 21 km (13 mi) deep clouds of sulfuric acid
photos moved by 334 km/h (220 mph) winds. The mission also plans
Jun 2, 1983 Venera 15 U.S.S.R. Radar mapper to study the Venus greenhouse effect and volcanic activity of the
Jun 7, 1983 Venera 16 U.S.S.R. Radar mapper past and present, if any.
Dec 15, 1984 Vega 1 U.S.S.R. Venus/Comet
Halley probe
MARS
Dec 21, 1984 Vega 2 U.S.S.R. Venus/Comet
Halley probe Mars has always attracted attention because of its unique,
bright reddish color. The properties and surface characteris-
May 4, 1989 Magellan U.S. Orbital radar
mapper tics have also attracted attention, particularly since Mars
Oct 18, 1989 Galileo U.S. Flyby seems to have similarities to Earth. It orbits the Sun at an
measurements average distance of about 1.5 AU. It makes a complete or-
and photos bit every 687 days, about twice the time that Earth takes. Mars
Apr 11, 2006 Venus Express ESA Orbital rotates in 24 hours, 37 minutes, so the length of a day on Mars
spacecraft is about the same as the length of a day on Earth. The observa-
Jun 5, 2007 MESSENGER U.S. Flyby photos tions that Mars has an atmosphere, light and dark regions that
appear to be greenish and change colors with the seasons, and
white polar caps that grow and shrink with the seasons led to
Venus, like Mercury, has no satellites. Venus also does not early speculations (and many fantasies!) about the possibilities
have a magnetic field, as might be expected. Two conditions of life on Mars. These speculations increased dramatically in
seem to be necessary in order for a planet to generate a magnetic 1877, when Schiaparelli, an Italian astronomer, reported seeing
field: a molten center part and a relatively rapid rate of rotation. “channels” on the Martian surface. Other astronomers began
Since Venus takes 243 days to complete one rotation, it is the interpreting the dark greenish regions as vegetation and the

382 CHAPTER 15 The Solar System 15-6