The 10-cent Mariner 10 commemorative stamp was issued on April 4, 1975, at Pasadena, California. It paid the domestic first-class rate for letters weighing less than half ounce. The stamp shares numerous design elements with USA Scott 1556, and while they have different designers and dates of issue, the two are catalogued together under the heading "U.S. Unmanned Accomplishments in Space."
Engineered to explore the orbits of Venus and Mercury, Mariner 10 launched in November 1973. The mission's two- year plan used the gravitational pull of Venus to reach Mercury. The probe also used solar winds to help with locomotion when fuel ran low. Mariner 10 orbited the planets in the opposite direction of Earth's orbit.
Mariner's first photographed images, which revealed Venus's dense cloud cover, reached NASA scientists in February 1974. Data collected by Mariner 10 helped determine Venus's rotation period and use of Earth's magnetic field. Photos of Mercury revealed its cratered surface and its large scarps and plains. Research also recorded its radical temperature variations between night and day.
Designed by Roy Gjertson, the Mariner 10 stamp was printed at the Bureau of Engraving and Printing on the Giori presses.
"Mariner 10." National Space Science Data Center. http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1973-085A (accessed September 3, 2008).
U.S. Space Objects Registry. http://188.8.131.52/oes/search/index.cfm?fuseaction=search.display (accessed July 7, 2008).
Kloetzel, James E., ed. 2006 Specialized Catalogue of United States Stamps & Covers. 84th ed. Sidney, Ohio: Scott Publishing Co., 2005.