Why man instead of machine?

George Washington University's Dr. Logsdon has argued that national prestige can still be harnessed as a powerful motivator for pushing humanity's presence farther into space. Indeed, the shuttle program itself owes its existence in large part to President Nixon's desire to avoid going down in history as the president who pulled the plug on the manned spaceflight program after he canceled Apollo, historians say.

For Lori Garver - a former NASA associate administrator and someone who nearly landed a slot on one of Russia's tourist trips to the space station - it's important to take a long-term view.

"We have to learn to be a multi-planet species to survive," she says. "It could be centuries before we have a requirement like an incoming asteroid" or some other disaster. "But we have to get started."

As if to punctuate her point, astronomers have been tracking asteroid 2004 MN4, which will pass within 22,600 miles of Earth in 2029 - just inside the orbits of geostationary satellites. Approaches by an asteroid this large - roughly 1,000 feet across - are rare, occurring about once every 1,300 years, astronomers say.

Even without the cold war, the ideological symbolism of manned spaceflight cannot be ignored, adds Robert Zubrin, president of the Mars Society. He holds that an ideological battle is still being fought between the West and its remaining "totalitarian enemies" and "radical fundamentalists." Human space exploration, particularly sending humans to Mars, would represent a declaration of "the power of reason, courage, and freedom ... in handwriting large enough that no one will need spectacles to read it," he writes in The New Atlantis, a science and technology policy journal.

Over the long term, he says in an interview, humans will naturally move into space, just as early humans left Kenya's rift valley to populate the planet.

"We'll break out of the 'valley' when we build our first Jamestown on Mars," he says. "If we break out of the valley, 500 years from now we'll occupy many worlds. When humanity looks back 500 years from now, no one will care who rules Iraq." They will, however, celebrate their Jamestown.

April 12, 1961

Yuri Gagarin (right), first human in space, Vostok 1 Program.

May 5, 1961

Alan Shepard, first American in space, Mercury 1.

February 20, 1962

John Glenn, first American to orbit Earth.

June 16, 1963

USSR's Valentina Tereshkova, first woman in space.

January 27, 1967

Americans Virgil Grissom, Edward White, and Roger Chaffee die in preflight test, Apollo 1.

July 16, 1969

First humans to land on the Moon:AmericansNeil Armstrong and Buzz Aldrin, Apollo 11.

April 11, 1970

Service-module explosion causes deep space abort. Crew returns safely (right), Apollo 13.

December 19, 1972

Final Apollo lunar mission returns, Apollo 17.

April 12, 1981

First piloted orbital test flight of US space shuttle.

June 18, 1983

First flight of US female astronaut, Sally Ride.

August 30, 1983

First flight of African-American astronaut, Guion "Guy" Bluford.

January 28, 1986

Challenger shuttle explodes moments after takeoff, killing the entire crew, including the first civilian on a NASA mission, schoolteacher Christa McAuliffe.

September 12, 1992

Mae Jemison, first African-American woman in space (right).

March 22, 1995

Russsian Valeriy Polyakov sets space endurance record: 438 days aboard Mir space station.

October 29, 1998

At age 77, US Sen. John Glenn (left) becomes oldest person to travel into space.

August 28, 1999

Sergei Avdeyev sets record for total time spent in space: 747 days in three missions.

April 30, 2001

Dennis Tito serves as the first "space tourist" after paying $20 million to accompany Russian space officials as a guest.

February 1, 2003

Columbia explodes during reentry. US grounds shuttle.

October 15, 2003

China becomes third nation capable of manned spaceflight, launching Lt. Col. Yang Liwei (above) into orbit.

Sources: Spaceflight: A Smithsonian Guide; CBSNews.com

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