Q&A: How to (theoretically) spot an alien

Are we alone in the universe? The answer to one of humanity’s biggest questions is complicated by a basic reality: If there is life on other worlds, it may not look familiar. A sample of rocks from Mars or another planet almost certainly won’t have recognizable fossils or another similarly obvious sign of living organisms, said Mikhail Tikhonov, an assistant professor of physics in Arts & Sciences at Washington University in St. Louis who studies microbial communities.

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