What's more, many worried that NASA would get bogged down in the gray lunar dust and fail to move on toward the Red Planet.
That's part of why the Obama administration shifted the focus from the moon to a "flexible path" that would target new destinations, such as an asteroid, to get astronauts farther out into deep space.
But the asteroid mission proved more difficult than expected. Eventually, NASA proposed having a robot haul a boulder from an asteroid and put it in orbit around the moon, where astronauts would rendezvous with the space rock. The so-called Asteroid Redirect Mission didn't receive very enthusiastic reviews from the space community or Congress, and this year it got the ax.
NASA has recently been working on plans for something called the Deep Space Gateway, an outpost in orbit around the moon.
And at the behest of Congress, the space agency has been building a giant new rocket and a deep space capsule. The vehicle is supposed to have its first test flight in 2019, when it will send an uncrewed capsule up to orbit the moon before returning to Earth.
Officials in the Trump administration asked NASA to consider putting humans on that flight, but NASA ultimately decided against it after a review. The first mission with a crew on that NASA spacecraft isn't supposed to happen until 2022.
The company SpaceX is also constructing a large rocket and has announced that it intends to launch the first private mission to the moon in 2018. SpaceX says it has paying customers for a trip in an automated capsule that wouldn't land, but would loop around the moon and then return.
SpaceX also has contracts with NASA to bring astronauts up to the International Space Station and is scheduled to start doing that next year as well. The company has already been hauling cargo to and from the station for NASA.
Boeing also has a space transportation system in the works, and its first flight with NASA astronauts on board is planned for 2018.
If those companies' efforts pan out, their space taxis will be the first vehicles to carry up astronauts from U.S. soil since the retirement of the space shuttles.