Since July, NASA’s Perseverance rover has drilled and collected four slim cores of sedimentary rock, formed in what was once a lake on Mars. They are the first of this type of rock to be gathered on another world—and scientists are excited because at least two of the cores probably contain organic compounds.

On Earth, organics, which are carbon-containing molecules, are often associated with living things, although they can be formed without the involvement of organisms.

Adding to the buzz over the rock samples, Perseverance collected them from an ancient delta in Mars’s Jezero Crater, where a river once deposited layers of sediment—and possibly other matter. River deltas on Earth often teem with living organisms. If life ever existed in Jezero, these cores are probably NASA’s best chance of finding it.

Having the cores is “fantastic”, if scientists ever hope to answer that question, says Tanja Bosak, a geobiologist at the Massachusetts Institute of Technology in Cambridge.

In the coming years, NASA and the European Space Agency plan to send other spacecraft to Jezero to pick up the cores that Perseverance has collected and bring them back to Earth, where scientists will analyse them with advanced laboratory techniques. The samples, which are expected to arrive no earlier than 2033, will be the first ever returned from Mars.

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