Venus is no place for a walkabout.  With a surface temperature hundreds of degrees hotter than a restaurant pizza oven, atmospheric pressure equivalent to being 3,000 feet underwater, and noxious “air” that is 96.5% carbon dioxide, its environment is about as hostile as can be imagined.  But that doesn’t mean we haven’t been able to find other ways to learn a lot about our “sister planet.”  In fact, Venus was the first planet visited by spacecraft from Earth.

A Mariner Sails By

More than half a century ago, in December 1962, Mariner 2 flew by Venus at an altitude of just over 21,600 miles.  The probe’s hexagonal main body was tiny by today’s standards – just over 39 inches (yes, inches) in diameter – but it was stuffed with instruments to detect the distribution of surface temperatures, to make rudimentary analyses of the Venusian atmosphere, and to transmit observations of the interplanetary environment during its journey.

President John F. Kennedy (right) receives model of Mariner 2 from NASA officials in 1961. (Image credit: NASA)

Unfortunately, Mariner 2 carried no cameras to provide a photographic record of the historic mission (and, by the way, to boost its public relations value), but it was nonetheless a milestone in our exploration of the inner Solar System.  And it would be followed by a virtual parade of unmanned spacecraft from Earth.

"Venera" in Russian

Through the 1960s, the U.S. and the Soviet Union were engaged in a high-stakes “space race.”  The U.S. poured most of its resources into the overarching goal of landing astronauts on the Moon, while also establishing the Mariner planetary exploration program.  The U.S.S.R. sent a series of cosmonauts into orbit around Earth, but chose not to compete with the U.S. to be first to land men on the Moon.  Rather, it increasingly prioritized the launch of unmanned missions to the Moon, Venus, and Mars.

“Can we put a man on the moon before them?” — President John F. Kennedy to Vice President Lyndon B. Johnson, April 1961

The Soviets launched the Venera 1 mission more than a year before Mariner 2’s successful visit, but a serious malfunction prevented the spacecraft from transmitting data back to Earth – and, of course, confirming that it had actually accomplished its fly-by mission.  However, the U.S.S.R. achieved remarkable later successes with the Venera program.

Surface of Venus from Venera 13.

From, 1967 to 1969, three Venera spacecraft reached Venus and collected data on its environment, both at the surface and aloft.  Beginning with Venera 7, in 1970, eight of the program’s probes landed on the planet, vastly increasing our understanding of the planet.  While Venus may have truly been Earth’s sister planet billions of years ago, it has evolved over eons to become a scorched planet where no life we can imagine could possibly survive.

Venera 9 provided a kind of visual confirmation of this view when it transmitted the first images from the surface of Venus, in 1975.  At the feet of the lander was the rocky rubble of a hellish world, the sort of place to which those with a religious mindset might imagine the damned would be consigned for eternity.  High above, Venera 9’s orbiter even detected signs of thunder and lightning (fire and brimstone?) in the atmosphere.  Perhaps the planet should have been named Hades instead of Venus.

Lavinia Platinia on Venus from NASA's Magellan spacecraft. (Image credit: NASA/JPL)

The Flow of Missions Slows to a Trickle

The Venera program concluded, in 1983, and was followed by two Vega missions to Venus before the Soviet Union collapsed, in 1991, taking its planetary exploration program with it into history.

NASA sent several Mariner spacecraft to Venus in the 1960s and 1970s, and followed up with the Pioneer Venus Project, which launched two separate missions (Pioneer Venus Orbiter and Pioneer Venus Multiprobe), in 1978.  Eleven years later, NASA capped its missions dedicated solely to Venus with the Magellan mission, which mapped at least 70% of the surface of the planet.  Since then, NASA has collected additional data from a number of missions that flew by the planet (using it for gravity assisted acceleration) on their way to other primary objectives.

Part of Eistla Regio on Venus as depicted in 3-D by Magellan spacecraft. (Credit: NASA/JPL)

In the 21st century, Russia and the U.S. have been joined by China, Japan, and the European Union as players – and only Europe (Venus Express) and Japan (Akatsuki) have launched missions to Venus since the turn of the century.  Perhaps because few still believe our “sister planet” could be habitable to life or hospitable to a visit by humans, Venus seems to have little remaining allure to explorers.  Maybe it just seems dead to us.