The Martian atmosphere is about to stop being such a drag on a Colorado-built spacecraft. By January 11th, controllers will stop dipping the 2001 Mars Odyssey into the Red Planet’s dusty atmosphere — a process called aerobraking that is used to slow a spacecraft and round out its orbit without using precious fuel. The 11 weeks of maneuvers have shortened Odyssey’s lap time from 18 1/2 hours, when it went into Martian orbit on Oct. 23, to just under two hours.