Most rare coins experts expect these to become the most valuable modern coins ever sold, Stack's Bowers Galleries claimed.

The mission, STS-93, most prominently helped deploy the Chandra X-Ray Observatory, according to NASA.

It also made history as the first to be commanded by a woman, Air Force Col. (ret.) Eileen Collins.

A group of gold commemorative coins that traveled into orbit aboard recently fetched a series of historically high bids at auction.

Ever since a collection of Sacagawea dollars made the cosmic journey in 1999 aboard shuttle Columbia, the gold coins have been "hidden, shrouded in secrecy, and locked away in America’s most secure location: Fort Knox in Kentucky," California-based auction house Stack’s Bowers Galleries said in .

That was until recently, when the U.S. g

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