Making a case for humans in space.

Donald Kennedy and Brooks Hanson ("A time of opportunity," Editorial, 30 Jan., p. 589) clearly are aware of the extraordinary foundation of scientific knowledge about the origin and history of the Moon, Earth, planets, and solar system that came as a consequence of U.S. explorations of the moon. I was surprised, however, by their implication that the time of human exploration of space has passed because it has become too costly. I would submit that the rising costs of human exploration are a consequence of a government monopoly and not an inherent fact of space operations. An investordriven space effort rather than a policyand politics-driven space effort would force costs down instead of up.