Early this year, NASA announced that its Perseverance rover had found organic molecules on Mars by shining a laser through samples collected in Jezero Crater, adding to the rover Curiosity's finds in 2018. But Curiosity and Perseverance’s discoveries of organic molecules on the Martian surface could just be the tip of the iceberg.

According to a newly published paper in Science Advances, a team working with the European Space Agency’s EXPOSE-R2 system on the International Space Station have found that the technique Perseverance used might have trouble finding many molecules to detect. After exposing the sorts of organic molecules most easily detected by the technique — known as Raman spectroscopy after Indian physicist C.V. Raman, who discovered it nearly a century ago — to a simulated Mars in Earth orbit, only a few traces of life remained at the surface.

But there might be a gold mine for astrobiologists beneath the probes’ wheels — it’s just that rovers haven’t been able to dig deep enough to get at it.

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