The moon may have been the entire world for a day for Apollo 11 astronaut Buzz Aldrin 40 years ago, but today he hopes the United States and the world set their sights on a far grander goal: Spreading humanity to Mars and perhaps asteroids and comets.

But NASA's plan to replace its three aging space shuttles with Orion capsules to carry astronauts to the moon by 2020 may not justify its $35 billion cost if it stops there, said Aldrin, one of the first humans to set foot on the moon during the Apollo 11 landing on July 20, 1969.

Instead, the United States can aid international partners in exploring the moon and free up its own spaceflight resources to develop systems for even more ambitious goals, he told in an interview.

"While the international explorers, with our help, are going to the moon, we can develop the long-duration life support systems for other things," said Aldrin, 79. "Flying by a comet, visiting an asteroid and station-keeping with it."

Mars within reach

With an international base on the moon and vital technologies like in-space refueling, Aldrin envisions an ambitious series of expeditions to send astronauts on a deep space mission to visit the asteroid Aphophis when it swings near Earth in 2021. A temporarily manned base on the Mars moon Phobos could follow, he added.

"By that time, we'd be ready to put people in a gradual permanence on Mars by 2031," Aldrin said. "That, in a nutshell, is what I really think we should be doing."

NASA's current transition from the space shuttle to Orion is a huge step backward, Aldrin said. The shuttle's may not have lived up to its initial expectations, but its ability to haul tons of cargo to orbit and land on a runway is a capability that should not be lost in order to replace it with something faster and cheaper, he stressed.

"What happens to U.S. space global leadership if everything is going to be done on the cheap and we're not going to think ahead, and we're going back to the moon for some reason that really won't justify the cost of human habitation," he said.

The United States should "do the things that this nation can do and strive toward maintaining globally space leaderships. And that means lifting bodies, runway landers and not going back to the moon, because we've been there," Aldrin added.

The moon at heart

While the future of American spaceflight remains to be seen, Aldrin said he takes comfort knowing that the history-making Apollo 11 moon landing still resonates today.

"I'm kind of glad it does," he said. "Whatever we do in space is not on the front page unless there's something going wrong or it's highly unusual. And it doesn't capture the budget discussion."

Aldrin and Neil Armstrong spent a day on the lunar surface and just 2 1/2 hours walking outside their Eagle lander. Their crewmate Michael Collins orbited overhead inside the command module Columbia. Five other Apollo moon landings followed.

In the past, Aldrin has frankly recounted the depression and bout with alcoholism that followed his flight aboard Apollo 11.

Now, 40 years after the mission, he said he's matured considerably since the flight - his last space mission and has released a new autobiography "Magnificent Desolation." In a bid to spark interest in spaceflight in today's youth ad children, he rapped about the moonshot with Snoop Dogg and Talib Kewli, and has a new children's book about space exploration.

The Apollo 11 anniversary, he said, is a chance for NASA to remind the American public of the country's technical prowess.

"I do think that it does momentarily keep the public abreast of what we're doing now, and they'll look back," Aldrin said. "Of course it's been a long time, so many people weren't alive when those things happened, and those that were are, I guess, maturing a little bit and look back with a bit of nostalgia."

But the moon, Aldrin added, hasn't changed.

"Well, it still looks about the same when I look at it," Aldrin said. "But I know inside, it sounds kind of trite, that it's really not the stranger that it was. It's somewhat of a friend now because I've been there."

Aldrin said he still vividly remembers that first moonwalk. Armstrong called the view beautiful, but it was so much more. Aldrin, instead, saw what described as magnificent desolation.

"Beautiful, I thought, that's not quite right," he said. "It's magnificent that we're here ... but what a desolate place this was."

He still recalls the apparent stillness.

"No life, no motion, no air. And just the same uniform color of all the dust that reflected light differently depending on the angle of the sun and your view," Aldrin said. "It just wasn't a very welcome place at all."

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