The unmanned Mariner 10 space probe swings past the planet Venus at a distance of less than 4,000 miles, its cameras capturing a completely opaque sphere whose clouds reveal no surface. But when viewed through ultraviolet filters, Venus suddenly reveals an immense amount of atmospheric detail. Mariner 10’s UV views of Venus are the best images available until the dual Pioneer Venus mission of the late 1970s; meanwhile, Mariner 10 speeds past the planet en route to Mercury.
