In Alei et al. 2022, the fifth paper of the LIFE series (link to arXiv) we explore the potential of LIFE for characterizing emission spectra of Earth at various stages of its evolution. Assuming a distance of 10 pc and a Sun-like host star, we simulated observations obtained with LIFE on eight different scenarios, which correspond to cloud-free and cloudy spectra of four different epochs of the evolution of the Earth. We then performed Bayesian retrievals on each scenario.
With the nominal spectral resolution (R =50) and signal-to-noise ratio (assumed to be S/N=10 at 11.2 microns), we can identify the main spectral features of all the analyzed scenarios (most notably CO2, H2O, O3, and CH4). We conclude that the baseline requirements for R and S/N are sufficient for LIFE to detect O3 and CH4 in the atmosphere of an Earth-like planet with an O2 abundance of around 2% in volume mixing ratio. Doubling the S/N would allow a clearer detection of these species at lower abundances. This information is relevant in terms of the LIFE mission planning.