For most of the past half-century, scientists have been trying—and failing—to find life on Mars. Beginning with NASA’s twin Viking landers, which touched down on the Red Planet in 1976, this hunt has focused on discovering possible biosignatures—organic molecules that may indicate life’s past existence.

There are, of course, good reasons to suspect the search will ultimately prove successful. Although now inhospitably dry and cold, a wealth of evidence shows that Mars was once a warmer, wetter and more habitable world. Life may have flourished there billions of years ago. Presumably, an epochal discovery could come from using a robot-borne chemistry lab to tease some telltale organic molecules out of an appropriate sample scoured from the right rock. But as highlighted in a recent study published in Nature Communications, this task may be too much for even our best present-day Mars explorers, NASA’s Curiosity and Perseverance rovers. Perhaps evidence for life on Mars is hidden in plain view, merely unrecognized because of the limits of rocketry and current rover technology, and a breakthrough will only come if—or when—we manage to either bring bits of Mars back to Earth or send astronauts to the Red Planet.

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