2011 44¢ Messenger Mission
Issue Date: May 4, 2011
City: Kennedy Space Center, FL
Printed By: Banknote Corporation of America
Printing Method: Offset, Microprint "USPS"
The Mariner 10 mission of 1973 brought back a wealth of knowledge about Mercury – our Solar System’s innermost planet. However, with this information, scientists came up with new questions about the planet that would be answered best by putting a spacecraft in orbit around Mercury.
On August 3, 2004, Messenger departed Earth on its journey through the inner Solar System. The space probe’s mission included one flyby of Earth, two flybys of Venus, and three flybys of Mercury, before its orbit around Mercury beginning March 18, 2011.
Among the mission’s goals was to get the first images of the whole planet and gather detailed information on the makeup and form of its crust. Scientists also hoped to learn more about Mercury’s geological history, its thin atmosphere and magnetosphere, and its core and polar materials. They took special interest in these because Mercury has the highest density and thinnest atmosphere of the planets and is thought to be the only other Earth-like planet with a global magnetic field.
The three flybys of Mercury produced images of more than 95% of the planet. A July 2008 flyby revealed the presence of water in Mercury’s upper atmosphere, a shock to all involved in the project. Scientists could only imagine what other unexpected discoveries would be revealed once Messenger completed its mission in 2012.