The Oxygen Bottleneck for Technospheres

TL;DR

This paper argues that a substantial atmospheric oxygen level, specifically at least 18%, is crucial for the development of advanced technospheres and detectable technosignatures on exoplanets, linking oxygen presence to technological evolution.

Contribution

It introduces the concept that only planets with high oxygen partial pressure can develop detectable technosignatures, emphasizing oxygen's role in technological evolution beyond biosignatures.

Findings

Oxygen partial pressure ≥ 18% is necessary for open-air combustion.

Oxygen is the most likely atmospheric component for technological development.

High oxygen levels are a key prior for technosignature detection strategies.

Abstract

As oxygen is essential for respiration and metabolism for multicellular organisms on Earth, its presence may be crucial for the development of a complex biosphere on other planets. And because life itself, through photosynthesis, contributed to creating our oxygen-rich atmosphere, oxygen has long been considered as a possible biosignature. Here we consider the relationship between atmospheric oxygen and the development of technology. We argue that only planets with substantial oxygen partial pressure ($p_{\rm O_2}$) will be capable of developing advanced technospheres and hence technosignatures that we can detect. But open-air combustion (needed, for example, for metallurgy), is possible only in Earth-like atmospheres when $p_{\rm O_2}\ge 18\%$. This limit is higher than the one needed to sustain a complex biosphere and multicellular organisms. We further review other possible planetary atmospheric compositions and conclude that oxygen is the most likely candidate for the evolution of technological species. Thus, the presence of $p_{\rm O_2}\ge 18\%$ in exoplanet atmospheres may represent a contextual prior required for the planning and interpretation of technosignature searches.