Illustration: A piloted flyby spacecraft releases a robotic probe (Venera 4) into the cloudy atmosphere of Venus. / NASA
The U.S.S.R.’s Venera 4 was the first spacecraft to return data from inside another planet’s atmosphere
If Venus’s pass across the sun earlier this week yields a bounty of information for hunters of transiting worlds in other planetary systems, it’s because Venus is a known entity. Studying the June 5 Venus transit as if it were a faraway exoplanet “gives us a reality check,” says planetary physicist Colin Wilson of the University of Oxford. “We can check on all those exoplanet techniques to see how accurate they really are.” Such data may enhance NASA’s Kepler mission as well as the many ground-based campaigns using planetary transits to identify distant worlds, a method that has led to the discovery or characterization of more than 200 exoplanets.
That reality check would not be possible without the data planetary scientists already have about Venus. And humanity’s up-close exploration of Earth’s cloud-shrouded closest neighbor began in earnest 45 years ago, when the Soviet probe Venera 4 launched on June 12, 1967.
The first two Veneras had failed after launch. Venera 3, launched in 1965, is thought to have crashed on Venus but returned no data.
At last, on October 18, 1967, Venera 4 became the first man-made object to enter another planet’s atmosphere and send back data. “It was before any Mars landers or anything,” Wilson says. And it changed our view of Earth’s sister planet forever.