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Visits to Venus
On 7th February 1961, Russia, which was known as the Soviet Union back then, was the first country to attempt to send a space probe to Venus. The probe sent into space was called Sputnik 7. When it was in orbit around Earth, a space craft called Venera would have been launched from it to travel to Venus and land on the planet. However, something went wrong with the ignition and the space craft never left Earth orbit. Slightly more successful was Venera 1, which was launched from Sputnik 5 while in orbit around Earth on the 12th February 1961. This mission was going to be a flyby mission, meaning that it was going to fly by Venus, and send back information about the planet. It was never intended to land on the planet. Venera 1 began its journey to Venus but after 7 days and at about 2 million kilometres from Earth, contact with the space craft was lost. The spacecraft did eventually come within 100,000 kilometres of Venus. Later Russian attempts were made with Venera 2 which was launched on 12th November 1965 and Venera 3, launched on 16th November 1965. Venera 2 was another flyby mission and it did reach Venus, coming within 24,000 kilometres of the planet, but again the spacecraft systems weren't operating so no information could be sent back. Venera 3 was a lander mission, meaning that it was intended to land on the surface of the planet. The space craft did succeed in landing on Venus, but once again, the communications systems failed so no information could be sent back. But Venera 3 was successful in that it became the first manmade object from Earth to land on Venus. The Russians continued to attempt to send probes to Venus over the next few years and finally succeeded in 1967.
Mariner 2 spacecraft (image credit: NASA)
In 1967, both Russia and America reached Venus again. Russia landed their Venera 4 space probe on the planet on 18th October, and NASA's Mariner 5 mission completed a fly by on the 19th October. The Venera 4 lander was the first successful mission to send data back from below the clouds of Venus. Information about the amount of oxygen and hydrogen in the planet's atmosphere, how much radiation the planet received from the Sun and the pressure on the planet was sent back to Earth while the Venera 4 lander capsule parachuted through the planet's atmosphere. Before this mission, scientists believed Venus to be similar to Earth, and thinking that the planet's surface may have hills and oceans. Venera 4 was designed to communicate while underwater. However, Venera 4 stopped communicating after 94 minutes of its descent when it was about 24 kilometres above the surface, probably due to the intense heat and pressure on Venus. NASA's Mariner 5 was actually designed to go to Mars, but wasn't needed because Mariner 4 successfully went there instead. So, NASA modified it and sent it to Venus. Mariner 5 was designed to orbit Venus. It reached the planet a day after Venera 4 had landed there, and sent back more information about the planet's atmosphere, confirming that it is 85-99% carbon dioxide.
After 1967, the USA turned most of its attention to the Moon and didn't actually return to Venus until 1973, and that was actually for a mission to Mercury which passed Venus on the way which will be described later. The Russians continued to persevere, sending Venera 5 and Venera 6 to the planet in January 1969, again landing on the planet but communications failing during the descent to the planet's surface. On 17th August 1970, Venera 7 was launched. It entered Venus' atmosphere on 15th December 1970 and successfully sent back signals for 23 minutes after landing on the planet. These were the first signals ever sent to Earth from the surface of another planet, even though they were very weak. Venera 8 also successfully sent back signals from the planet when it arrived there on 22nd July 1972, using a refrigeration system to keep the lander probe cool during its descent, and measuring the level of light on the planet, discovering that it was similar to the level of light on Earth on an overcast day and therefore suitable for photography. This paved the way for future missions which would take the first images from the surface of the planet (maybe scientists didn't think to install a flash on the camera!)
In 1973, the USA returned to Venus, but only in passing! Mariner 10's main goal was to reach Mercury, the closest planet to the Sun in the Solar System. Mariner 10 is one of only two space craft to have visited Mercury so far. The other is Messenger which entered into an orbit of Mercury in March 2011. To get to Mercury though, they needed the help of Venus. Mariner 10 pioneered a new method of getting around the Solar System. In order to get to Mercury, the space probe used the gravity of Venus to propel it to the next planet. It did this by being sent from Earth to Venus, and when it reached Venus, was pulled in by the planet's gravity. The space craft builds up speed as it orbits Venus which is travelling at 35 kilometres a second around the Sun, and is then propelled to its next target. The means that the space craft actually uses velocity rather than fuel to travel around space, which is handy seeing as there are no fuel stations in space! This method is called Gravity Assist, or the Slingshot Effect. Since then, gravity assist has become standard in space travel. Voyager 2 managed to visit all four of the Gas Giants in the 1970s and 1980s using gravity assist! Mariner 10 was a technical nightmare with systems constantly failing as it made its journey to Mercury via Venus. However, it successfully took the first close up images of Venus and returned more information about the planet before leaving for Mercury. The picture to the left was taken by Mariner 10 and is now over 30 years old.
Although Mariner 10 successfully returned pictures of Venus as it passed, images from the planet's surface had still not been received. This was to change when, on 8th and 14th June 1975, Russia launched Venera 9 and Venera 10. These space crafts had probes which descended into the planet's atmosphere and, when they landed on the planet's surface on the 22nd and 25th October 1975, took the first images and sent them back to Earth, shown below.
The first images from the surface of Venus - taken by Venera 9 and Venera 10
These images are distorted, giving a "fish-eye" view of the planet. They showed shadows on the planet, rocks that were about 30 to 40 cm in size and signs of lava or weathered rocks. Missions to Venus continued by the Russians throughout the rest of the 1970s and in the 1980s. Venera 13 took more images of Venus when it arrived on the planet in 1982, including the first colour pictures. Below is an image taken by Venera 13, showing the planet's fine soil and flattened (or pancake) rocks.
The final Russian Venera missions were Venera 15 and Venera 16 which were both launched in 1983. The Venera missions were not the only missions attempted by Russia to visit Venus. The Zond missions ran from 1964 to 1970. Although most of these were designed for exploration of the Moon, Zond 1 was launched towards Venus on 2nd April 1964 while in orbit around Earth. Although systems failed on 14th May, the space craft flew by Venus on 14th July. The Vega mission was launched in 1984, designed to visit Halley's comet, which was due to come close to Earth in 1986. Two Vega craft were launched on 15th and 21st December 1984. They reached Venus in June 1985, using the gravity of the planet to propel them to Halley's Comet in a similar way to Mariner 10's mission to Mercury. However, when they arrived at Venus, two lander probes were launched from the Vega spacecraft and landed on the planet, sending back more information about Venus' atmosphere and surface conditions. The Vega probes themselves continued on to Halley's Comet, reaching it in 1986.
Venus from Pioneer 12
Magellan on Space Shuttle Atlantis
Other missions which visited Venus were NASA's Galileo mission, launched in 1989, and the NASA/European Space Agency/Italian Space Agency Cassini-Huygens mission, launched in 1997. Both of these missions were actually going to Jupiter, but visited Venus to build up momentum, using the gravity assist method mentioned earlier. Galileo sent more information back about Venus' clouds, and Cassini-Huygens tried to detect lightning on Venus. The first suggestion of the possibility of lightning on Venus was reported during a Russian Venera mission in the 1970s, but Cassini-Huygens found no evidence of lightning during its visit.
On 9th November 2005, the European Space Agency launched its first probe to Earth's nearest neighbour. Named Venus Express, the space craft is very similar to ESA's Mars Express which visited Mars in 2003 and is currently in orbit around the planet. It actually contains spare parts from Mars Express and the European Space Agency's Rosetta space craft. Venus Express arrived at Venus in April 2006 and ended its mission by falling into its atmosphere in 2014.
Other proposed future missions to Venus include NASA's Venus In-Situ Explorer and Europe's Venus Entry Probe, both planned for around 2022. Russia are also considering launching Venera-D for 2024. All of these missions involve elements of landing on the surface of Venus to make observations and conduct experiments. Well, it's been a while since the last mission landed there.
Before 1961, Venus, like the other planets in the Solar System, was a mystery to people on Earth. But it was probably the one planet that people believed to be most similar to Earth. It is the nearest planet to Earth, is a very similar size, its name means Beauty and, from Earth, it shines brightly in the night sky. The swirling clouds probably covered a surface of hills and mountains, trees and flowers, grass and water; a planet suitable for life. However, when the first space craft arrived at Venus, it soon became obvious that Venus was not quite the Earth-like planet it seemed. The atmosphere was discovered to be poisonous, and space crafts designed to land on Venus were simply destroyed by the intense heat and immense pressure as they got closer to the surface. The Russians persevered with their Venera missions and did eventually land a probe on Venus and successfully managed to take pictures from the planet's surface, whereas the Americans concentrated on exploration of the Moon and Mars. Even so, today we have a good idea about the atmospheric make-up of Venus, we know that life simply can't exist there, and we finally know some of the secrets of what lies below the cloud cover. People will never visit Venus, but will always be able to see its deceptive beauty in the night sky.