If humans ever get to Mars, what might they do there" Would they use spare weapons-grade plutonium to heat up the red planet to a more Earth-like temperature, as one fanciful-sounding plan suggested"

Probably not, according to Humboldt Man Dell, a former chief of NASA's Mars programmes.

But he said a favoured Mars exploration plan could be considerably quicker than the White House proposal for a moon base to be used as a stepping stone for a human mission to our next-door planetary neighbour.

Some NASA officials wondered privately before Wednesday's announcement why they had been left out of discussions about the presidential programme.

Still, Man Dell, a 40-year NASA veteran who left a year ago to become a research fellow at the University of Texas Centre for Space Research, said the US space agency has the technical know-how to accomplish the moon and Mars missions, though not necessarily as the White House envisions.

For a start, Man Dell said in a telephone interview that while a permanent moon base was possible, it would double the cost of any human mission to Mars.

"I have no objection to building a moon base, but if you're going to go to Mars, the cheapest way to do it is to base it on the Earth and then make Mars the second safest place in the solar system for humans, and then send the humans to Mars,"Mandell said.

He said there would be "logistical nightmares"lurking in the plan to transport equipment and humans to the moon and then launch a mission to Mars from there.

"With one-third of the NASA budget, in six or seven years you could be at Mars,"Mandell said. "It doesn't compute with me to try to drag it out."

18 months on Mars

A faster method "ranging in price from US$20 billion to US$100 billion as opposed to an earlier NASA estimate of about US$400 billion "would be to build a beachhead on Mars before humans arrive, he said.

"The right way to do this job is to build a little village there before you ever send humans,"Mandell said. "You'd put Winnebago-size (bus-size) payloads there and they would connect to each other robotically."

These payloads would include living quarters, hospital and kitchen, he said.

This would include a plant to produce water from the ice that might be available beneath the martian surface. The water would be for human use during the mission, and could then be split into hydrogen and oxygen to fuel the trip back to Earth, according to Mandell.

This scenario estimates a six- or seven-month travel time from Earth to Mars, an 18-month stay and another six or seven months for the voyage home.

The space shuttle fleet, grounded since the fatal Columbia accident on February 1, 2003, would have only a small role in this plan, carrying crew members to the Mars craft as it moved in Earth orbit, Mandell said. The Mars vessel would go from Earth orbit to Mars.

Apollo veteran excited

The last man on the moon, Eugene A. Cernan, said he knew he wouldn't hold that distinction forever.

"I've been waiting for this day for 31 years,"said Cernan, who was in the audience when Bush outlined his proposal to continue America's journey into space with manned missions to the moon, to Mars and to worlds beyond.

Bush singled out Cernan and quoted what the astronaut said when he left the lunar surface: "We leave as we came, and God willing as we shall return, with peace and hope for all mankind."

Cernan, now 69, was commander of the Apollo 17 mission and set foot on the lunar surface in December 1972.

Cernan said that when he returned to Earth, he believed that America would someday launch new missions to the moon: "I said we're not only going to go back to the moon, we'll be on our way to Mars by the turn of the century."

Although Bush did not set a timetable for a Mars mission, aides said it would be later this century, sometime after 2030.

The Apollo 17 mission was Cernan's third space flight.

Bush's new initiative

The following are the highlights of Bush's new space proposal he announced on Wednesday:

Current programmes:

Return the space shuttle to flight and fulfill the US commitment to the International Space Station.

Halt most work on the space station by 2010, confining the American role there to studies of the health effects of space flight.

Retire the space shuttle fleet around the same time.

Next generation:

Increase the use of robotic explorers throughout the solar system.

Start developing a new "Crew Exploration Vehicle"for venturing beyond Earth's orbit; test it by 2008 and launch its first mission by 2014. Use it to shuttle astronauts to the space station.

Send unmanned probes to the moon by 2008.

Return Americans to the moon between 2015 and 2020.

Establish a long-term presence on the moon to serve as a launching area for "human missions to Mars and to worlds beyond."

Costs:

Bush offered no overall price tag for the new ventures; his aides declined to provide one.

(China Daily 01/16/2004 page7)