Magellan

Magellan, deployed from the Space Shuttle Atlantis in May 1989, was the first planetary spacecraft launched from the shuttle. Arriving at Venus in 1990, it spent four years peering through the planet’s permanent cloud deck with synthetic aperture radar, mapping 98 percent of the surface at resolutions that revealed towering volcanoes, pancake domes, and vast lava plains — but strikingly few impact craters.

That young surface implied Venus had been resurfaced by global volcanism within the last billion years, transforming scientific understanding of how Earth’s twin went so wrong. Magellan ended its mission in 1994 with a deliberate plunge into the Venusian atmosphere, pioneering the ‘aerobraking’ techniques later used at Mars.