Space.com is reporting that:
THURSDAY, AUGUST 11, 2005
Launch of the Mars Reconnaissance Orbiter has been officially reset for Friday morning. The launch team will start a fresh countdown this evening, leading to liftoff at 7:43 a.m. EDT (1143 GMT).
The Mars Reconnaissance Orbiter will join three other satellites currently in orbit around Mars. It will take higher resolution photos than any mission previous to this, and has ground penetrating radar to look for water. It also will be able to send data back at a much faster rate than previous interplanetary spacecraft.