When it comes to exploration, robots can outperform astronauts at a far lower cost and without risk of human life.  Why, then, do so many people conceive of space exploration as the domain of humans rather than robotic explorers? Martin Rees and Donald Goldsmith explore why robots are the future of space exploration.

How much do we need humans in space? How much do we want them there? Astronauts embody the triumph of human imagination and engineering. Their efforts shed light on the possibilities and problems posed by travel beyond our nurturing Earth. Their presence on the moon or on other solar-system objects can imply that the countries or entities that sent them there possess ownership rights. Astronauts promote an understanding of the cosmos and inspire young people toward careers in science.