Odyssey’s aerobraking around Mars could be a trick or treat event. If all goes as planned, the spacecraft will begin dipping into the Martian atmosphere about a week after the probe is inserted into Mars orbit — that is, around Halloween. Data gleaned by the already-orbiting Mars Global Surveyor is set to help Odyssey snuggle up into a correct science orbit. “We may want to ‘pop up’ if a storm appears and spreads quickly. We always want an orbit that will not decay and plunge us into Mars before we can do a maneuver,” said Steve Saunders, JPL Mars Odyssey Project Scientist.