On March 1, 1981, Venera 14, unmanned Soviet planetary probes, landed on Venus and transmitted information to the earth. It analyzed Venus’s atmosphere, detected certain long-lived radioactive isotopes (chiefly uranium and thorium), sent back the first close-up photographs of the planet’s surface, and mapped the surface of the northern hemisphere with radar (by Venera 15 and 16, the last two of the series).
Venus is 42 million kilometers away from the earth and is similar to earth in volume, weight and specific gravity.