Space not only can be but must be explored, with missions to the moon, Mars, and ultimately to planets circling other stars in the nearby universe, according to Stephen Hawking, the world-renowned astronomer.

His comments, made just over one year ago to an audience in Washington, D.C., are a counterpoint to those telling President Obama that the U.S. space program isn’t worth it, that it’s expensive, that these are tough economic times with other pressing needs of the moment, and why must the United States explore the heavens, anyway?

Obama’s detailed plans for funding NASA and U.S. space efforts in the fiscal year ending Sept. 30, 2010, will be unveiled next month. His budget will reveal whether the only nation that placed men on the moon, still the richest nation on Earth, will continue to lead in space, or forfeit the final frontier to other countries.

Hawking’s clarion call for a robust space effort clearly opts for the former alternative.

A year ago, on April 21, 2008, Hawking — possessed of one of the greatest minds of our age — set forth why space exploration is worth it, even at great expense. He spoke to an audience at the George Washington University, before the Elliott School of International Affairs – Space Policy Institute, an appearance co-sponsored by Lockheed Martin Corp. [LMT]. He spoke with a computer-generated voice.

Although his Herculean intellect is trapped within the confines of a body increasingly paralyzed by amyotrophic lateral sclerosis (Lou Gehrig’s Disease), the irony is that he is one of the greatest authorities on the infinite space of the universe, and its infinite possibilities.

A British subject schooled at Oxford and Cambridge, he holds many of the highest academic and professional honors that the United Kingdom can bestow.

(For a ver batim rendering of his remarks prepared by Space & Missile Defense Report, please see partial transcript in this issue.)

Hawking first examined how life can emerge anywhere in the universe, and explored whether the human race is alone in possessing intelligence, in the vastness of billions of stars and planets.

Life appeared on Earth rather suddenly, in astronomical and biological-evolutionary terms, suggesting either that life can form independently with relative ease, or that life on Earth may have come from another place, he said. Meteors have come to Earth from Mars, and perhaps other places, he noted.

It is possible that life could form independently on planets circling different stars, he said, and also possible for life to emerge separately on two different planets in the same stellar system, though that would be pressing the limits of probability.

Still, it is worth going to explore other worlds, especially if they contain water, he said.

Water (hydrogen and oxygen) can provide water to drink and for irrigating crops, oxygen to breathe, and hydrogen for heating, electricity and vehicle power. Nuclear and solar panels also can be used.

Travelers spending half a year or so at a time on the International Space Station show that extended trips into space are feasible and survivable, though they inevitably entail physical damage to the health of those travelers, the punishing effect of weightlessness and space radiation.

Hawking said an outpost on the moon not only is feasible, it can be a way station for sojourners to other parts of the solar system, such as Mars.

He also addressed the question as to why, if there is intelligent life elsewhere in the nearby universe, it hasn’t contacted residents of Earth.

Three possibilities come to mind, Hawking said: there may not be any life, at least not nearby. Or, there may be life on a planet in the solar system or a nearby stellar system, but it may never have evolved to intelligent life. Or, intelligent life did develop, reaching roughly the current stage of human development, so that it finally was able to create nuclear weapons and destroy itself.

"Let’s hope this is not the reason we have not heard from anyone," Hawking said, half joking.

Then Hawking set forth his final thesis: long-term space travel is not only feasible, it is imperative.

Mars: The Next Target

"Mars is the obvious next target," after moon missions, he said. To be sure, he added, life on Mars would be no visit to Club Med.

Mars "is half as far again as the Earth from the sun, and so receives half the warmth. It once had a magnetic field, but it decayed 4 billion years ago, leaving Mars without protection from solar radiation. This stripped Mars of most of its atmosphere, leaving it with only 1 percent of the pressure of the Earth’s atmosphere. However, the pressure must have been higher in the past, because we see what appear to be runoff channels and dried-up lakes. Liquid water cannot exist on Mars now. It would vaporize in the near-vacuum. This suggests that Mars had a warm, wet period, during which life might have appeared, either spontaneously or through panspermia," the introduction of life there that originated somewhere else.

Why examine Mars? "There is no sign of life on Mars now, but if we found evidence that life had once existed, it would indicate that the probability of life developing on a suitable planet was fairly high," Hawking said.

He cited the unmanned missions that NASA has sent to Mars, and the incredible wealth of discoveries that they have provided to Earthlings. How much more could be reaped from manned missions.

Finally, he said mankind should reach for the stars, though he said interstellar travel may not occur for two to five centuries.

Chances are that an Earth-like planet lies out there, reachable in 30 years going at the speed of light, he indicated.

"Our observations indicate that a significant fraction of stars have planets around them," he noted. "So far, we can detect only giant planets, like Jupiter and Saturn, but it is reasonable to assume that they will be accompanied by smaller, Earth-like planets. Some of these will lie in the Goldilocks zone, where the distance from the stars is in the right range for liquid water to exist on their surface. There are around a thousand stars within 30 light years of Earth. If 1 percent of these had Earth-sized planets in the Goldilocks zone, we have 10 candidate new worlds," Earth-like planets.

Astronauts won’t be walking on those planets in the next 20 or 30 years, but someday it could happen.

"We can’t envisage visiting them with current technology, but we should make interstellar travel a long-term aim," Hawking said. "By long-term, I mean over the next 200 to 500 years. The human race has existed as a separate species for about 2 million years. Civilization began about 10,000 years ago, and the rate of development has been steadily increasing. If the human race is to continue for another million years, we will have to boldly go where no one has gone before."

Just how such path-finding, unprecedented explorations will occur if the United States goes miserly and de-funds space programs, however, he didn’t examine. (Please see story on pending NASA budget cuts in this issue.)