“Two centuries ago, Meriwether Lewis and William Clark left St. Lois to explore the new lands acquired in the Louisiana Purchase,” George W. Bush said, announcing his desire for a program to send men and women to Mars. “They made that journey in the spirit of discovery... America has ventured forth into space for the same reasons.” Yet there are vital differences between Lewis and Clark’s expedition and a Mars mission. First, Lewis and Clark were headed to a place amenable to life hundreds of thousands of people were already living there. Second, Lewis and Clark were certain to discover places and things of immediate value to the new nation. Third, the Lewis and Clark venture cost next to nothing by today’s standards. In 1989 NASA estimated that a people-to-Mars program would cost $ 400 billion, which inflates to $ 600 billion today. But the fact that a destination is tantalizing does not mean the journey makes sense, even considering the human calling to explore. And Mars as a destination for people makes absolutely no sense with current technology. Present systems for getting from Earth’s surface to low-Earth orbit are so fantastically expensive that merely launching the 1,000 tons or so of spacecraft and equipment a Mars mission would require could be accomplished only by cutting health-care benefits, education spending or other important programs or by raising taxes. Absent some remarkable discovery, astronauts, geologists and biologists once on Mars could do little more than analyze rocks and feel awestruck beholding the sky of another world. It is interesting to note that when President Bush unveiled his proposal, he listed these recent major achievements of space exploration: pictures of the rings of Saturn and the outer planets, evidence of water on Mars and the moon of Jupiter, discovery of more than 100 planets outside our solar system and study of the soil of Mars. All these accomplishments came from automated probes or automated space telescopes. Bush’s proposal, which calls for “reprogramming” some of NASA’s present budget into the Mars effort, might actually lead to a reduction in such unmanned science, the one aspect of space exploration that’s working really well. Rather than spend hundreds of billions of dollars to hurl tons toward Mars using current technology, why not take a decade or two decades, or however much time is required researching new launch systems and advanced propulsion? If new launch systems could put weight into orbit affordably, and if advanced propulsion could speed up that long, slow transit to Mars, then the dreams of stepping onto the Red Planet might become reality. Mars will still be there when the technology is ready. The drive to explore is part of what makes us human, and exploration of the past has led to unexpected glories. Dreams must be tempered by realism, however. For the moment, going to Mars is hopelessly unrealistic. George Bush’s comparison of Lewis and Clark’s expedition and a Mars mission is mentioned