41 years ago, on June 12, 1967, a modified R-7 rocket lifted off from deep within the Soviet Union carrying a spacecraft to another world. The spacecraft was Venera 4, and it was on its way to Venus. Venera 4 was not the first spacecraft to arrive at Venus. That honor goes to the American Mariner 2 spacecraft, launched in 1962. But, Mariner 2 just flew by Venus. Venera 4 was destined to actually enter the planet’s atmosphere.

As the name implies, Venera 4 was not the first spacecraft...