A stronaut Don Pettit says he would hop on a spaceship to Mars tomorrow if one were available. Despite returning earlier this year after 51/2 months in orbit, the Oregon native said he’d be excited about heading for the Red Planet. “We’ve demonstrated that there are no barriers for human physical performance for a trip to and landing on Mars,” said Pettit, who is in Oregon this week to promote the nation’s manned spaceflight program.