President Bush is scheduled to announce this week new destinations for U.S. astronauts. In a speech Wednesday, he is expected to order the space agency NASA to send people back to the moon and eventually to Mars and beyond.
After a three decade hiatus, the United States is again setting its sights on the moon.
The last humans to touch lunar soil were the Apollo 17 astronauts in December 1972. But two years before they even left the launch pad, President Richard Nixon's budget cuts ordained the end of the Apollo program three missions short of its scheduled 20 flights.
At the time, NASA had plans for a super launch rocket 45 stories high with extra engines strapped onto its first stage. It was to be used to establish the first moon base when the Apollo series of missions was over.
Now, President Bush has resurrected the notion of a lunar base. It would become a launch pad for outbound missions to Mars or asteroids.
A supporter of human space exploration, Brian Chase of the National Space Society, says the moon makes sense as a first step toward deeper solar system missions because it is so near.
"The moon is much closer to the Earth than Mars is. It can serve as a test bed for future exploration techniques," he said. "The other reason is that there are a lot of resources on the moon that can be valuable to developing a new space economy and eventually actually producing some products that can be of benefit right here on Earth."
Because the moon has only one-sixth of Earth's gravity, launches from there would require less energy.
A former chief of exploration at NASA, Michael Griffin, supports the outward migration of humans from Earth, but he says going to the moon before Mars has disadvantages as well as advantages.
"The pros in support of a lunar base would that that is where you learn how to survive for long periods of time on other planetary surfaces and be only three days away from home when things go wrong, as they inevitably will," he said. "The cons are that it is money spent in a direction not as interesting as Mars."
In fact, some experts believe revisiting the moon would only divert time and resources from a human journey to Mars. The president of the Mars Society, Robert Zubrin, says the United States should bypass the moon altogether.
"What should the goal be? It should be humans to Mars," he said. "Mars is where the science is, Mars is where the challenge is, and Mars is where the future is. However, it shouldn't be humans to Mars in 50 years. It should be humans to Mars in 10 years."
Mr. Zubrin says humans can roam farther and dig deeper for evidence of past life on Mars than robotic vehicles can. Brian Chase of the National Space Society agrees.
"Humans can always learn more on the ground than a robot can. The sense of intuition and the sense of one's understanding of one's environment is something that can't be built into a robot," he said.
But Duke University historian Alex Roland, a former NASA historian, argues that the presence of astronauts actually decreases the scientific benefits of a mission. In addition, he says humans increase the cost of a space journey 10 times.
"Whenever people are put on a spacecraft, its mission changes. Instead of exploration or science or communication or weather, the mission of the spacecraft becomes life support and returning the crew alive," he said. "This limits where the spacecraft can go, how much equipment it can carry, how long it can stay, what risks it can take."
Clearly, this is not the advice President Bush is following. As White House officials have explained prior to his announcement, he envisions a human presence on the moon by the year 2015 and on Mars perhaps a generation after that.