Two State quarter dollars made their closest approach to the dwarf planet Pluto at shortly after 11:49 UTC July 14, fulfilling a journey of some 3 billion miles that the two coins started on Jan. 19, 2006.

The two coins are aboard the New Horizons spacecraft, the first human vessel to visit Pluto.

See previous coverage of New Horizons and Curiosity missions:
Spacecraft carrying State quarter reawakens
1909 Lincoln, V.D.B. cent on Mars

Pluto is the last of the original nine planets to be visited by mankind (Pluto was reclassified as a dwarf planet in 2006, a few months after the New Horizons mission was launched). Because of the distance to Pluto and the mechanics of planetary alignments, it likely will be many decades before another mission is sent to visit the planetary body.

When New Horizons was launched in January 2006, the special contents it carried aboard were a closely guarded secret. It was not until a September 2008 ceremony to induct a New Horizons model into the Smithsonian National Air and Space Museum Udvar-Hazy Center space science collection that it was revealed that the craft carried a small cargo of souvenirs, including a pair of State quarter dollars.

As Coin World reported Dec. 8, 2014: "The coins are a Florida quarter dollar to represent the state where New Horizons was launched and a Maryland quarter dollar, representing the state where the craft was built. The coins also serve a utilitarian purpose; they are being used as a spin-balance weight on the 10-year mission."

The New Horizons spacecraft is not the only NASA probe to carry numismatic materials aboard it. The Curiosity rover on the surface of Mars carries a 1909 Lincoln, V.D.B. cent on board.