Astronauts stranded for two extra months aboard the International Space Station after the shuttle Columbia accident showed that humans are strong enough to make the long trip to Mars, one of the expedition’s members said on Monday. Donald Pettit, one of three members of the station’s Expedition Six, said he and his two crew-mates who spent 161 days on the space station inadvertently demonstrated humans’ fitness for interplanetary travel. Pettit said the demonstration was not planned, but said Expedition Six demonstrated “that there are no barriers for human physical performance to a trip to and a landing on Mars.”