Asked how long it could be before astronauts land on Mars, Arthur Thompson, mission manager for MER surface operations, told Reuters in an interview in Lima, "My best guess is 20 to 30 years, if that becomes our primary priority."

"If". Unfortunately, I don't see credible manned exploration given a high priority by NASA. Let's hope that private space development can give us the kickstart we need to do things like this in the near future!