This is because, on Earth at least, relatively complex, long-chain carbon molecules are involved in biology. Source: NASA/JPL-Caltech/MSSSThe organic molecules found by Curiosity consist of carbon atoms linked in long chains, with other elements bonded to them, like hydrogen and oxygen. Among the molecules were decane, which has 10 carbon atoms and 22 hydrogen atoms, and dodecane, with 12 carbons and 26 hydrogen atoms. Mars Sample Return will deliver Mars rocks to Earth for study. Mars Sample Return would do this with the samples already gathered by the Perseverance Mars rover.