Venera 13, a Soviet spacecraft, was the first lander to transmit color images from the surface of Venus. Although other landers arrived before and after it, pictures from Venera 13 tend to be more widely circulated because they are in color.
The spacecraft was designed to last about half an hour on Venus' harsh surface, but sent back data for more than two hours after its landing March 1, 1982.
Since no lander has ventured on to Venus since the 1980s, the Venera program's images of the surface stand as the best close-up record of the planet today.
Shrouded in secrecy
Documentation on the Venera program is sparse because it took place in the Soviet Union. More formally known as the Union of Soviet Socialist Republics, this entity is the predecessor of today's Russia and surrounding nations. The union dissolved into independent states in 1991.
Unlike the United States' public space program, the Soviet Union preferred to keep information about their spaceflights private until officials deemed it appropriate to release the news. This is why Sputnik, for example, shocked the Western world when it launched Oct. 4, 1957. Few people in the United States realized that the Soviets were capable of sending satellites into space.
The Soviets kept plans for other achievements private until the milestones were accomplished. Some prominent examples include the April 12, 1961, flight of the first man in space, Yuri Gagarin, and the first spacewalk by Alexei Leonov on March 18, 1965.
It should be noted that over time, American astronauts and Russian cosmonauts became great friends and shared information. The two nations also had a symbolic mission together in space in July 1975 called the Apollo-Soyuz Test Project.
Still, there are aspects of the Soviet program that have not been released publicly – Venera information among them. For some Venera missions, it's still not clear what sort of instruments flew on them.
For example, of Venera 11, a NASA web page notes, "It is unknown whether the lander probe carried an imaging system. No mention of it occurs in the Soviet literature examined by the author. Two other experiments on the lander did fail, and their failure was acknowledged by the Soviets. Some U.S. literature on the subject notes that the imaging system 'failed' but did return some data."
Early Venus exploration
The primary goal of Venera was to learn more about the planet Venus. Astronomers once saw the planet as Earth's twin, and some science fiction writers fantasized about advanced life living below its clouds.
Today we understand that the planet is a hothouse of pressure-filled atmosphere, capable of crushing an unshielded probe very quickly. Temperatures on Venus can get as high as 870 degrees Fahrenheit (465 degrees Celsius).
But it would take space-age probes to reveal more about the second-closest planet to the sun.
Both NASA and the Soviet Union reached for Venus in the early days of their space program in the 1960s, but were hampered by a series of failed probes.
After the failure of Mariner 1, NASA's Mariner 2 became the first spacecraft to fly by Venus on Dec. 14, 1962, and revealed a hot planet under high pressure, with unbroken clouds shrouding the surface.
The Soviets had their first successful Venus mission in 1967 – with Venera 4 – after several failed attempts to reach the planet. On Oct. 18, 1967, Venera 4 became the first probe to transmit information back while entering the atmosphere of Venus.
From there, the Soviets began to experience more success. Venera 7 made a soft landing and sent back data on Dec. 15, 1970, the first spacecraft to do so. It transmitted information for 23 minutes on the surface before succumbing to the heat and pressure. Five years later, Venera 9 was the first to send back a picture from the surface.
Venera 13 launched Oct. 30, 1981, aboard a Proton rocket from the Baikonur Cosmodrome (located in today's Kazakhstan). The spacecraft carried several instruments on board, including spectrometers, a drill and surface sampler and a panoramic camera.
After a four-month journey to Venus, the descent portion of the spacecraft separated from its bus and plunged through the clouds towards the surface. After entering the atmosphere, Venera 13 popped a parachute and rode it all the way down.
Venera 13 touched down safely on March 1, 1982, in the southern hemisphere on Venus, on an area that the Lunar and Planetary Institute describes as "a typical expanse of Venusian plains." The broad area around the landing site is known now to contain lava flows and small dome volcanoes, which would indicate a very active surface.
"The [Venera 13] landing site appears smooth but broken, and topped around the lander itself by abundant debris of various sizes," read an article in Science News published March 20, 1982.
"U.S. researchers looking at the photos suggested that the smooth areas might be either solid slabs of rock, or a crust of fine particles cemented together by chemical activity of the atmosphere. Such 'fines' could be dust transported by the wind, or perhaps weathered from the underlying bedrock itself by chemical erosion."
The color images from the spacecraft are widely used today in books, magazine articles and websites about the planet Venus. The pictures only show a tiny bit of the sky in the corners, and focus on the surface in front. The spacecraft is visible at the bottom, along with a discarded lens cover.
In some versions, the surface looks yellow, but scientists say it is difficult to figure out what the "true color" on Venus' surface is because the clouds filter out blue light.
Venera 13 also extended a drilling arm to the surface, picked up a bit of Venusian regolith, and analyzed it inside a sealed chamber. The spacecraft also kept track of parameters such as the depth the drill reached, and the speed of the drilling rig, to get more information about the surface's physical makeup.
"The results showed that the surface characteristics correspond to compacted ash material such as volcanic tuff [rock]," NASA wrote.
The spacecraft stayed in touch with Earth through the orbiting bus, which relayed its findings back to controllers in the Soviet Union. After 127 minutes on the surface, Venera 13 succumbed.
The Soviet Union sent three more Venera spacecraft to Venus. Venera 14, a twin of Venera 13, launched five days later and also reached the surface. It lasted there for 57 minutes. Venera 15 and Venera 16 subsequently orbited Venus together and sent back information between 1983 and 1984.
While other spacecraft have visited Venus in the decades since (NASA's Magellan spacecraft is a notable example), no other machines have ventured onto the surface since the Venera spacecraft.
Until humanity sends a spacecraft there again, Venera 13 will stand as a spacecraft showing one of the best views of the ground of Venus.
— Elizabeth Howell, SPACE.com Contributor