Venus (left) was long considered to be Earth's twin. Because of the cloud cover, it was also a planet of mystery. Many science fiction writers pictured it as a luxurious rain forest. Probes to Venus have revealed it to be very hot, turbulent, and possessing a deadly acidic atmosphere.

Mercury (right) has proven to be very scarred and battered.

Venus

• Sputnik 7 (USSR)  4 February 1961. Attempted Venus impact. A faulty ignition timer caused the craft to remain in Earth orbit.
• Venera 1 (Gamma, Venus 1) (USSR) 12 February 1961. Attempted flyby. Communications lost en route, 19 February 1961. On 19-20 May 1961, Venera 1 passed within 100,000 km of Venus and entered a heliocentric orbit.
• Mariner 1 (USA)  22 July 1962. Attempted flyby. Veered off course at launch and was destroyed by range safety.
• Sputnik 19 (Sputnik 23, Alpha Pi 1) (USSR)  25 August 1962. Attempted lander. Escape stage failed and it reentered the atmosphere on 28 August 1962.
• Mariner 2 USA) 27 August 1962. Successful fly-by of Venus. Now in solar orbit. Closest approach was 34,773 km on 14 December 1962.
• Sputnik 20 (1962 Alpha Tau 1, Sputnik 24) (USSR)   1 September 1962. Attempted lander. Escape stage failed and it reentered the atmosphere.
• Sputnik 21 (Alpha Pi 1, Sputnik 25) (USSR)  12 September 1962. Attempted flyby. Third stage exploded, destroying the craft.
• Cosmos 21 (USSR)  11 November 1963.   Either a Venera test flight or an attempted flyby. Never left Earth orbit, decayed 3 days later.
• Venera 1964A (USSR)  19 February 1964. Attempted flyby. Launcher failed and never acheived Earth orbit.
• Venera 1964B (USSR)  1 March 1964. Attempted flyby. Launcher failed and never acheived Earth orbit.
• Cosmos 27 (USSR)  27 March 1964. Attempted flyby. Acheived Earth orbit, but failed to reach escape orbit.
• Zond 1 (USSR) 2 April 1964. Flyby mission, communications failed 14 May 1964 before arriving at Venus. Flew by Venus on 14 July 1964 at a distance of 100,000 km. Now in solar orbit.
• Venera 2 (Venus 2) (USSR)  12 November 1965. Flyby mission. Spacecraft passed Venus at a distance of 24,000 km on 27 February 1966. Communications lost before arrival. Now in solar orbit.
• Venera 3 (Venus 3) (USSR)  16 November 1965. Lander mission. Communications lost before entering planetary orbit, crashed into Venus 1 March 1966. Venera 3 was the first spacecraft to impact another planet.
• Cosmos 96 (USSR)  23 November 1965. Attempted lander. Reached Earth orbit. Damaged by a possible explosion during Venus transfer orbit. Reentered Earth's atmosphere 9 December 1965.
• Venera 1965A (USSR)  26 November 1965. Attempted flyby. Launcher failed.
• Venera 4 (Venus 4) (USSR)  12 June 1967. Entered the Venusian atmosphere on 18 October 1967. Signals were received until the craft had descended to 24.96 km.
• Mariner 5 ( Mariner Venus '67) (USA)  14 June 1967. Successful flyby to 4,000 km on 19 October 1967. Now in solar orbit.
• Cosmos 167 (USSR)  17 June 1967. Intended lander, stranded in Earth orbit and decayed 8 days after launch.
• Venera 5 (Venus 5) (USSR)  5 January 1969. Atmospheric probe. Crushed by Venusian atmosphere about 26 km above surface 16 May 1969. Returned data for 53 minutes.
• Venera 6 (Venus 6) (USSR) 10 January 1969. Atmospheric probe. Crushed by Venusian atmosphere about 11 km from the surface on 17 May 1969. Returned 51 minutes of data.
• Venera 7 (Venus 7) (USSR)  17 August 1970. Landed 15 December 1970, returned 23 minutes of data.
• Cosmos 359 (USSR)  22 August 1970. Possible lander, escape stage failed, leaving the probe in a geocentric orbit.
• Venera 8 (Venus 8) (USSR)  27 March 1972. Landed 22 July 1972, returned 50 minutes of data.
• Cosmos 482 (USSR)  31 March 1972.Posible atmospheric probe or lander. Failed to achieve velocity required for transfer to a Venus trajectory from low Earth orbit.
• Mariner 10 (USA)  3 November 1973. Returned data on the Venusian atmosphere before moving on to Mercury. Passe within 5768 km of Venus on 5 February 1974.
• Venera 9 (USSR)  8 June 1975. Lander returned data for 53 minutes, 20 October 1975.
• Venera 10 (USSR)  14 June 1975. Lander returned data for 65 minutes, 23 October 1975.
• Pioneer Venus 1 (Pioneer 12) (USA) 20 May 1978. Orbit achieved 4 December 1978, did radar mapping of the surface.
• Pioneer Venus 2 (Pioneer 13) (USA)  8 August 1978. Sent 4 probes into the atmosphere on 9 December 1978. Data returned was used to characterize the winds, turbulence, and propogation in the atmosphere.
• Venera 11 (Venera 11 Lander) (USSR)  9 September 1978. Orbiter and lander. Lander returned data for 95 minutes on 25 December 1978.
• Venera 12 (Venera 12 Lander) (USSR)  14 September 1978. Orbiter and lander. Lander returned data for 110 minutes on 21 December 1978.
• Venera 13 (Venera 13 Lander) (USSR)  30 October 1981. Orbiter and lander. Landed 1 March 1982, did soil analysis. The lander survived for 127 minutes.
• Venera 14 (USSR)  4 November 1981. Orbiter and lander. Landed 5 March 1982, did soil analysis. The lander survived 57 minutes.
• Venera 15  (USSR)  2 June 1983. Orbiter. Venusian orbit achieved. With Venera 16, it mapped Venus from the North pole to about 30° N latitude over an 8 month period.
• Venera 16 (USSR)  7 June 1983. Orbiter. Venusian orbit achieved. With Venera 15, it mapped Venus from the North pole to about 30° N latitude over an 8 month period
• Vega 1 (Venera-Halley 1) (USSR)  15 December 1984. Lander and baloon succeeded. 11 June 1985. The balloon floated in the atmosphere for 57 minutes and transmitted data. The lander did reach the surface and transmit data, however a strong wind jolt activated the experiments 20 km above the surface and no results were provided. Vega 1 continued on for a flyby of Halley's comet (6 March 1986).
• Vega 2 (Venera-Halley 2) (USSR)  21 December 1984. Lander and balloon succeeded, 15 June 1985. The balloon floated in the atmosphere for 46.5 hours and transmitted data. The lander did reach the surface and transmit data. Vega 2 continued on for a flyby of Halley's comet (9 March 1986).
• Magellan  (USA)  4 May 1989. Orbiter. Arrived 10 August 1990. Did radar mapping of 99% of the Venusian surface before burning up in the Venusian atmosphere 13 October 1994.
• Galileo (USA)  18 October 1989. Atmospheric probe to Jupiter. Passed Venus, passed Earth twice, and encountered three asteroids getting to Jupiter. It arrived at Jupiter in December 1995 and discovered a possible underground ocean on Europa. It was crashed into Jupiter on 21 September 2003, to avoid any possibility of a collision with a Jovian moon.
• Cassini (USA)  15 October 1997. Currently en route to Saturn. Cassini carries the Huygens probe to research the atmosphere of Saturn. Due to arrive on at Saturn June 2004. The craft is following a route similar to that of Galileo, passing Venus and Earth on its way to Saturn.
• Venus Express (ESA)  9 November 2003. Scheduled to enter orbit around Venus in April 2006.

Mercury

• Mariner 10 (USA)  3 November 1973. Flew past Venus, then on to Mercury. Photographed 57% of the surface of Mercury in 3 passes (704 km on 29 March 1974, 48,069 km on 21 September 1974, and 327 km on 16 March 1975). Now in solar orbit.
• Messenger (USA)  3 August 2004. Plans call for 3 flybys in 2008 and 2009, followed by a year long orbit of Mercury starting in March 2011.