NASA’s 2001 Mars Odyssey spacecraft has now entered the main aerobraking phase of the mission. “The initial phase of aerobraking has gone exceedingly well. By skimming through the upper reaches of the Mars atmosphere during each orbit, we have reduced our orbital period by more than three hours in the past two weeks,” said David A. Spencer, the Odyssey mission manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. Odyssey’s orbital period, the time required for the spacecraft to complete one revolution in its orbit around Mars, is currently 15 hours.