(CNN) On July 20, 1969, NASA put a man on the moon and captured it all on tape.

In 1976, the space agency unknowingly sold those tapes of original footage from the Apollo 11 lunar mission to a lucky intern who held onto them for decades. He never even knew their contents.

Now, NASA's blunder will belong to the highest bidder: the three surviving videotapes of the seminal moment in space exploration are up for auction--at a starting bid of $700,000.

According to Sotheby's , the tapes are worth up to $2 million. Bidding begins July 20, on the 50th anniversary of the moon landing.

The two-and-a-half hours of footage provide the sharpest image of the history-making mission ever recorded, from Neil Armstrong's first steps on the moon's surface to an interplanetary conversation with then-President Richard Nixon to the planting of the American flag.

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