The idea of sending people to Mars has been around for decades. It's been approached differently by different U.S. leaders and lawmakers. At this time, we don't have the technology to get people there and back. But scientists are working on it.
There's debate about whether it will be money well-spent, or if it's worth risking human lives when we could send robots. But one of the biggest restraints of a potential Mars mission could be a simple lack of desire.
RACHEL CRANE, CNN CORRESPONDENT: They say history is the best predictor of the future.
NEIL ARMSTRONG, AMERICAN ASTRONAUT: It's one small step for man —
CRANE: And historically, the U.S. has been the leader in space exploration.
HOUSTON MISSION CONTROL: They've got the flag up now. You can see the Stars and Stripes on the —
CRANE: But we're in different time, decades from the boundless Apollo era, when space exploration was a national priority.
JOHN F. KENNEDY, FORMER U.S. PRESIDENT: No nation which expects to be the leader of other nations can expect to stay behind in this race to space.
CRANE: Now, we're at a point where scientists and space enthusiasts say we need to push further.
CHARLES BOLDEN, NASA ADMINISTRATOR: We're closer to Mars today, humanity is, than we have ever been in the history of civilization.
CRANE: What are some of the lessons of the past that NASA is taking on these future missions to Mars?
BOLDEN: Some of the greatest lessons of the past have to do with our failures.
HOUSTON MISSION CONTROL: Obviously, a major malfunction.
BOLDEN: One of the things that we constantly remind ourselves is we have to be hungry all the time.
CRANE: What is it going to take to get to Mars?
BOLDEN: Blood, sweat, tears, some tragedy along the way, unfortunately. But the biggest thing, you know, the biggest thing is will power.
UNIDENTIFIED MALE: A beautiful view.
CRANE: Buzz Aldrin is the second man to walk on the moon and one of the most famous astronauts in history.
Going to Mars, it's going to be one of the biggest challenges humanity has ever taken on. Do you think we have the will to actually pull this off?
BUZZ ALDRIN, AMERICAN ASTRONAUT: No, we don't have the will right now. And the public is really not all that fired up.
KIP THORNE, PHYSICIST: The whole atmosphere that we're living in is not like it was in the Apollo era. One big difference is the level of enthusiasm of the American public. The second big difference is the level of enthusiasm in Washington.
CRANE: And it's not just enthusiasm. It's money, too.
During the Apollo era, though, NASA had about 4 percent of federal spending. Now, it's less than half of one percent. Is that going to have to change in order for us to pull off this mission?
BOLDEN: Yes, yes.
CRANE: NASA doesn't have an exact price tag for a manned mission to Mars. But some argue it could cost hundreds of billions of dollars. This year, NASA received a budget increase of $1.3 billion.
BOLDEN: The U.S. is trying to lead the rest of the world in exploring our solar system, but not a foray out and back, but actually expanding human presence throughout our solar system.
UNIDENTIFIED MALE: One step further on the moon.
CRANE: But historically, the U.S. wanted to do it alone.
BOLDEN: Going back to the beginning, international collaboration was non- existent. We got to the moon because of competition. We could not allow the Soviets to beat us to the moon.
CRANE: But it seems as though we've gone from the spirit of competition during the Apollo era to a spirit of collaboration and cooperation.
BOLDEN: And that's essential. We cannot do it alone. No nation can go where we want to go and do it alone. This is a human journey to Mars.