<ul><li>Nasa's Curiosity rover has found the largest organic compounds ever seen on Mars.</li><li>The material was found inside a 3.7 billion-year-old rock in Yellowknife Bay, which may have once been a habitable freshwater lake.</li><li>The discovery of these organic compounds suggests that Mars' organic chemistry might have reached the complexity needed for life to begin.</li><li>The next step is to bring all the rock samples back to Earth to settle the debate about life on Mars.</li></ul>

Major clue emerges in chance there was once life on Mars

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