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EDITORS: Norman H. Sleep is a professor of geophysics and, by courtesy, of geological and environmental sciences. A planetary scientist, Sleep studies the origin of the solar system and the conditions on early Earth that led to microbial life. His research has been published in Nature and other scientific journals. He was elected to the National Academy of Sciences in 1999.

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Re-thinking NASA's manned space program

It is time to rethink the manned space program. Despite the Columbia shuttle disaster on Saturday, which took the lives of seven astronauts, NASA officials have called for the shuttle program to continue. The cry, "Let's go on to Mars," has even been heard from some quarters in NASA.

What has post-Apollo manned space flight provided beyond adventure? There have been some scientific spin-offs, to be sure, but any large technical program -- even a more ill thought out one, such as trying to live at the bottom of the sea -- would have done that. The science contributions have been mostly targets of opportunity. For example, scientists have skillfully studied organisms in weightlessness. Extensive space sickness studies are necessary to keep the crew healthy. Yet no benefit to the 5 billion-plus people on the ground has come out of this work. No engineering application, such as making crystals or chemicals in space, has panned out. After 40 years, it is not too soon to ask for some practical results.

In contrast, unmanned satellites benefit everyone on Earth. One cannot turn on a television, make a long-distance phone call or turn on the Internet without having signals go through space. Weather satellites provide minute-to-minute worldwide coverage and timely warnings, and satellites image the ground motion around earthquake faults and volcanoes. Satellites also have revolutionized astronomy. No one would think of sending up people to get in the way of these applications. It would be like having a cloak-and-dagger guy aboard a spy satellite. Yet NASA has designed numerous robotic satellites to be launched from the shuttle including the much-vaunted Hubble Space Telescope, which was placed into orbit by astronauts aboard the shuttle Discovery in 1990.

Manned space flight in Earth orbit is inefficient, somewhat dangerous but not overwhelmingly expensive. Mars space flight is another story. The cost of getting people there and back is more than a trillion dollars -- yes, "trillion" with a "t." The popular and scientific interest in Mars is biology. Can we find evidence of living or fossil microbes? If not, can we catch the origin of life, frozen billions of years ago, in the act? A speck of organic dust or a live microbe would be a monumental discovery. A manned spacecraft with its life supports would risk contaminating Mars, which would likely defeat the scientific purpose of the mission.



By Norman H. Sleep

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