Bush -- speaking at the headquarters of the U.S. space agency NASA -- pledged to renew manned exploration of the moon by as soon as 2015. He also proposed setting up a permanent lunar base that would serve as launch point for future manned missions to Mars and other planets.
"We will build new ships to carry man forward into the universe, to gain a new foothold on the moon, and to prepare for new journeys to worlds beyond our own," Bush said.
He said the U.S.'s first priority would be to complete the International Space Station by 2010 and then to develop a new class of launch rockets that could carry robots and men to the moon. These would be the first manned flights to the moon since the last Apollo craft left the lunar surface some 30 years ago.
He gave no date for a manned Mars mission, but any such undertaking is still decades away.
Mark Hempsell, a lecturer in space technology at the University of Bristol in Britain, tells RFE/RL that there are many good reasons to send men to the moon -- both philosophical and practical.
"I am on record as having been one of those people who have said that [manned space exploration serves philosophical needs], but it's not really a matter of philosophy. It's a matter of sheer practicality. A sufficiently capable presence in space will enable us to deal with the problems that we have here on Earth on a very long-term basis. So, global warming, natural catastrophes, and all the other things that we are facing can be solved if we have a large enough space capability. And that certainly includes the moon," Hempsell said.
Bush's announcement comes as public interest in space appears to be growing, spurred by the recent successful landing of the U.S. unmanned "Spirit" probe on Mars. The probe is sending stunning pictures of the Martian surface to a general public who can see them simply by clicking on the Internet.
Hempsell says, however, that unmanned probes like the "Spirit" -- while valuable -- have only limited use. They can test the surface and atmosphere but cannot carry out extensive work.
Bush said manned flights to the moon make sense because astronauts there would mine the moon's natural resources. He said the resources could be used to make things like rocket fuel for an eventual flight to Mars. Bush said launching a rocket from the moon would be cheaper than from earth because of the moon's weaker gravity.
Richard Taylor, a space expert at Britain's "Probability Research Group," explains:
"Journeys to Mars cannot be done economically and sensibly from the surface of the earth. They have to be done from the moon, because only from the moon do the overall costs of building spacecraft, fuelling them, and powering them become acceptable," Taylor said.
Taylor adds that there are additional problems that could be solved on the moon, such as building reliable screens for crews against the peril of solar radiation during the six-month journey to Mars and another six months on the way back. Space suits and habitation modules could also be tested on the moon.
It's not clear yet if Bush's vision for U.S. space exploration will prevail. Even the first phases of the plan -- unmanned probes to the moon -- will costs many thousands of millions of dollars. And the U.S. government has now run up the biggest deficit in its history.
Bush's father, President George Bush, 14 years ago proposed a similar program to return men to the moon:
"For the new century -- back to the moon, back to the future, and this time back to stay," Bush senior said.
But his goal was eventually rejected by Congress, who found the costs prohibitive and the benefits questionable.
Space expert Hempsell, for one, says the venture is worth the money: "Bush's father, when he was president, also tried to start a Mars and moon initiative, but could not get political support. Let's hope his son has more success."