"I don't think we know anywhere as near as much as we think we do about the moon," he said in an interview with ABC News. "And I think that is true, I think we have just barely visited, what is often described as a flags and footprints mission, back in the '60s as part of the space race, we didn't go to the moon to learn about the moon."
Could we go to Mars? Certainly. But even NASA admits it would be too expensive for one country to do alone and we don't have the technology yet to make it happen. A round trip to Mars, barring a major advance in rocket technology, could take two years.
NASA engineers and planners are already working on that mission in a theoretical sense. But to solve the issues of propulsion and survival in interplanetary space takes money -- billions of dollars, money that just isn't in NASA's budget.
Lindsey, and other astronauts, who wouldn't be astronauts if they didn't believe in space exploration, say it is our destiny to go where no one has gone before.
The moon, Lindsey says, is the logical first step. "If we're going to ever go interplanetary, like to Mars , it sure would be a good idea to practice somewhere that's only four days away from the earth. The moon is in our future, we will go there. It's just a matter of time. And if we want to go to Mars, I think we have to go to the moon first."
(Additional reporting from ABC News' Jonathan Karl.)