Fifteen years of planning and 6 1/2 years of maneuvering in space will all come down to the crunch Thursday [March 17] evening as mission managers in Maryland try to slip NASA's Messenger spacecraft into orbit around Mercury.
The braking maneuver, playing out 96 million miles from Earth, will have to slow the desk-size planetary probe by 1,929 mph and ease it into a polar orbit around the planet closest to the sun.
Failure will leave Messenger's managers at the Johns Hopkins Applied Physics Lab near Laurel with less than 10 percent of the fuel the craft left Earth with, and limited options for recovery. And that would put the primary goal of the $446 million mission at risk.
But success will open the doors to at least a year of scientific discovery, yielding close-up, high-definition images, maps and data from a planet that until now has only been observed from Earth or during high-speed flybys. Those earlier visits were by Mariner 10 in 1974 and 1975, and by Messenger in 2008 and 2009.
