Non-detection of O/O informs frequency of Earth-like planets with LUVOIR but not HabEx
arXiv:2008.03952
Abstract
A critical question in the search for extraterrestrial life is whether exoEarths are Earth-like, in that they host life that progressively oxygenates their atmospheres roughly following Earth's oxygenation history. This question could be answered statistically by searching for O and O on exoEarths detected by HabEx or LUVOIR. The point of this paper is to compare the ability of HabEx and LUVOIR to prevent a false negative answer to this question, in which we do not detect O or O on any planet even if all exoEarths are Earth-like. Our approach is to assign O and O values drawn from Earth's history to a distribution of detectable exoEarths and determine whether O and O would be detectable using the Planetary Spectrum Generator. We find that if exoEarths tend to be Earth-like, we expect to detect O with a LUVOIR-sized instrument. We also find that LUVOIR is unlikely to have a false negative scenario in the context of searching for Earth-like life on its targeted exoEarths. Because of that, if LUVOIR does not detect O or O on any exoEarths, we will be able to constrain the maximum number of exoEarths that could be Earth-like. In contrast, we find that even if all exoEarths are Earth-like, HabEx has up to a 22% chance of not detecting O or O on any of them. This is because HabEx will detect less planets and cannot reliably detect O and O at all potential Proterozoic levels. This is a strong argument for building a larger telescope such as LUVOIR if we want to determine whether exoEarths tend to be Earth-like.
Must revise noise parameters used for HabEx