Syun Akasofu,in an opinion published in Eos , suggests using auroral spectra as a tool to detect extraterrestrial life. He argues that the green line of atomic oxygen at 557.7 nm wavelength is direct evidence for the existence of free oxygen in a planetary atmosphere. As the green line in the terrestrial aurora arises mostly from the fact that plants release abundant free oxygen into the atmosphere by the photosynthesis process, detecting an extraterrestrial aurora would indicate that the possibility of the presence of plant life is high. This idea is a good one because auroral spectra point to two key elements of the existence of life: atmospheric oxygen and a magnetic field. It also extends the search for extraterrestrial intelligence to the search for lower life forms.
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