A space telescope for infrared spectroscopy of Earth-like planets

Owen¹ has reviewed the potential for detecting life on Earth-like planets of nearby stars, from atmospheric spectra. The presence of oxygen, as revealed, for example, by the 7,600-Å absorption band, would be of particular significance. But even the direct detection of a Jupiter-like planet around the nearest star is a formidable task, perhaps just possible with the Hubble Space Telescope^2,3 or with a Michelson interferometer operating at 40-μ wavelength⁴. Earth-like planets, being fainter and closer in, are still more difficult. Here we show that a space telescope of 16 m diameter, apodized in a new way, could image and measure oxygen in the thermal infrared spectra of earthlike planets up to 4 pc away. Several interesting candidate stars lie within this distance.