摘要: One of the chief paradoxes molecular oxygen (O$_2$) is that it an essential requirement for multicellular eukaryotes on Earth while simultaneously posing a threat to their survival via formation reactive species. In this paper, constraints imposed by O$_2$ Earth-like complex life are invoked explore whether worlds with abiotic inventories can harbor such organisms. By taking major sources and sinks planets into account using simple model, suggested receive time-averaged X-ray extreme ultraviolet fluxes $\gtrsim 10$ times higher than might not be capable hosting lifeforms because photolysis molecules as water may lead significant buildup. Methods testing hypothesis searching anticorrelations between biosignatures indicators atmospheres described. event, however, successfully adapts high-oxygen environments, these could permit evolution large