Finding extraterrestrial life using ground-based high-resolution spectroscopy

TL;DR

Ground-based high-resolution spectroscopy offers a promising method to detect biosignatures like oxygen in exoplanet atmospheres, potentially enabling the discovery of extraterrestrial life without space telescopes.

Contribution

This paper demonstrates the feasibility of using ground-based telescopes and high-dispersion spectroscopy to detect atmospheric biosignatures in Earth-like exoplanets.

Findings

High-dispersion spectroscopy can separate planetary signals from telluric contamination.

Detection of oxygen in Earth-twin atmospheres is feasible with planned large telescopes.

Large arrays of flux collector telescopes could enable statistical studies of life-bearing exoplanets.

Abstract

Exoplanet observations promise one day to unveil the presence of extraterrestrial life. Atmospheric compounds in strong chemical disequilibrium would point to large-scale biological activity just as oxygen and methane do in the Earth's atmosphere. The cancellation of both the Terrestrial Planet Finder and Darwin missions means that it is unlikely that a dedicated space telescope to search for biomarker gases in exoplanet atmospheres will be launched within the next 25 years. Here we show that ground-based telescopes provide a strong alternative for finding biomarkers in exoplanet atmospheres through transit observations. Recent results on hot Jupiters show the enormous potential of high-dispersion spectroscopy to separate the extraterrestrial and telluric signals making use of the Doppler shift of the planet. The transmission signal of oxygen from an Earth-twin orbiting a small red dwarf star is only a factor 3 smaller than that of carbon monoxide recently detected in the hot Jupiter tau Bootis b, albeit such a star will be orders of magnitude fainter. We show that if Earth-like planets are common, the planned extremely large telescopes can detect oxygen within a few dozen transits. Ultimately, large arrays of dedicated flux collector telescopes equipped with high-dispersion spectrographs can provide the large collecting area needed to perform a statistical study of life-bearing planets in the solar neighborhood.