Signs of life

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Science  03 Nov 2017:
Vol. 358, Issue 6363, pp. 578-581
DOI: 10.1126/science.358.6363.578

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Finding evidence of life on a planet light-years away might seem impossible considering the distances involved. But astronomers hope that a true Earth twin, bursting with flora and fauna, would reveal its secrets to a distant observer. It won't be easy, considering the meager harvest of photons astronomers are likely to get from such a tiny, remote world, whose signal will be almost swamped by its much brighter nearby star. The new generation of space telescopes heading toward the launch pad, including NASA's mammoth James Webb Space Telescope, has only an outside chance of probing an Earth twin in sufficient detail. Astronomers are already dreaming of a future space telescope purpose-built to produce a crude image of an Earth-sized planet. To prepare for the coming flood of exoplanet data researchers are now compiling lists of possible biosignatures, from spectral hints of gases that might emanate from living things to pigments that could reside in alien plants or microbes.