People got very excited in 2004 when NASA’s rover Opportunity discovered evidence that Mars had once been wet. Where there is water, there may be life. … What could be more fascinating than discovering life that had evolved entirely independently of life here on Earth? Many people would also find it heartening to learn that we are not entirely alone in this vast, cold cosmos. But I hope that our Mars probes discover nothing. It would be good news if we find Mars to be sterile. Dead rocks and lifeless sands would lift my spirit.

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