By Christine McGourty
BBC science correspondent
The writer Ray Bradbury, author of The Martian Chronicles, is among those expressing unconditional joy at the suggestion of a manned mission to Mars.
The science fiction may soon become fact (Image by Nasa)
"We've been very lazy and stupid over the years," he told BBC News Online.
"We can't stay on Earth forever. We've got to move on. It's time we went to Mars to build a colony there.
The science fiction author says he has been in touch with the White House. "I've called President Bush to offer my help; so let's see if he responds."
Others are enthusiastic not so much about Mars, but about returning to the Moon.
Randy Wessen, mission scientist at the US space agency's (Nasa) Jet Propulsion Laboratory, in California, dreams of using the Moon to make the Earth a better place.
"Just think, we could move all our polluting factories there to help protect the environment here."
But there are many doubters, of course. Professor Bruce Murray, of the California Institute of Technology, says there is a danger that a base on the Moon could become an expensive diversion, much like the International Space Station, which he believes has been a costly and wasteful exercise that has kept astronauts from venturing beyond Earth orbit for many years.
As for the science to be carried out on the Moon, he maintains that is "not nearly as interesting as the science of the South Pole".
And Dr Andrew Coates, of the Mullard Space Science Laboratory at University College London, says the argument that the Moon could be a launch platform for missions to Mars does not hold water.
"To launch from the Moon isn't that easy. It has gravity," he says.
"It would make far more sense to have a platform in Earth orbit and go directly from there, rather than to go from the Moon."
The space advocacy group, the Planetary Society, has welcomed Bush's proposals. Louis Friedman, executive director of the society, told BBC News Online: "The human space programme has been bogged down in Earth orbit for many years, with no exploration, no pushing the frontiers of knowledge.
"Mars exploration would be a tremendous boost, far better than aimlessly drifting in space."
And there is relief at the announcement, finally, of the end of the space shuttle programme, which he described as "an albatross" round the neck of the US space programme.
But he is not so enthusiastic about a return to the Moon. "I like to say that we should go to the Moon first, but we already have. It's a backward-looking statement.
"Twenty-seven people have been to the Moon; more than 50 spacecraft have been there.
"The Moon's been explored. We know about the Moon. It's time we went further to really investigate the question of human destiny.
"Where is life going to take hold beyond Earth? Has it ever taken hold anywhere? And for that, we need to go to Mars."