  Oxygen is a promising exoplanet biosignature due to the evolutionary
advantage conferred by harnessing starlight for photosynthesis, and the
apparent low likelihood of maintaining oxygen-rich atmospheres without life.
Hypothetical scenarios have been proposed for non-biological oxygen
accumulation on planets around late M-dwarfs, where the extended pre-main
sequence may favor abiotic O$_2$ accumulation. In contrast, abiotic oxygen
accumulation on planets around F, G, and K-type stars is seemingly less likely,
provided they possess substantial non-condensable gas inventories. The
comparative robustness of oxygen biosignatures around larger stars has
motivated plans for next-generation telescopes capable of oxygen detection on
planets around sun-like stars. However, the general tendency of terrestrial
planets to develop oxygen-rich atmospheres across a broad range of initial
conditions and evolutionary scenarios has not been explored. Here, we use a
coupled thermal-geochemical-climate model of terrestrial planet evolution to
illustrate three scenarios whereby significant abiotic oxygen can accumulate
around sun-like stars, even when significant non-condensable gas inventories
are present. For Earth-mass planets, we find abiotic oxygen can accumulate to
modern levels if (1) the CO$_2$:H$_2$O ratio of the initial volatile inventory
is high, (2) the initial water inventory exceeds ~50 Earth oceans, or (3) the
initial water inventory is very low. Fortunately, these three abiotic oxygen
scenarios could be distinguished from biological oxygen with observations of
other atmospheric constituents or characterizing the planetary surface. This
highlights the need for broadly capable next-generation telescopes that are
equipped to constrain surface water inventories via time-resolved photometry
and search for temporal biosignatures or disequilibrium biosignatures to assess
whether oxygen is biogenic.
