The Soviet Union explores Venus starting with Venera 1 in 1961. The photo shows Venus as viewed by Venera 14 in 1982. /Courtesy of Donald Mitchell & Michael Carroll

Venus is called the "twin planet" of Earth. Venus is the closest to Earth in the solar system, and its size is similar as well. Its gravity is 90% that of Earth. Humanity has explored Venus since the early days of space development. The Soviet Union began exploring Venus with the probe Venera 1 in 1961. The photo shows Venus as viewed by Venera 14 in 1982. Venus has a temperature close to 500 degrees, and it has recently been revealed that there may be active volcanoes. The volcanic activity on Venus is believed to help understand the evolutionary process of Earth.