Dec. 10, 2018
Research Highlight

Lightning, Oxygen and Life Detection

A new study examines the role that lightning-produced catalysis could play in releasing oxygen in the atmosphere of extrasolar planets. On Earth, oxygen concentrations in the atmosphere are tied to life. Because of this, astrobiologists have been studying atmospheric oxygen as a potential biomarker of habitability on distant worlds. However, molecular oxygen (O2) and ozone (O3) can also be produced without biology.

Video screen capture of long-exposure photo of lightning strikes over water.
Video screen capture of long-exposure photo of lightning strikes over water.Image credit: NASA.

In order to avoid ‘false positives’ in the search for inhabited exoplanets, astrobiologists must thoroughly examine the abiotic processes that could produce oxygen in planetary atmospheres. By modelling the atmospheres of planets, astrobiologists can gain important insights into different atmospheric compositions that can result from biotic and abiotic processes on terrestrial planets. However, these models are not always in agreement about whether or not a given set of circumstances will produce a ‘false positive’ or not.

The recent study shows that some of the discrepancies in models could come down to how atmospheric and global redox balances are treated, and whether or not the effects of lightning are included. The authors of the study believe that the inclusion of lightning in models could help eliminate false positives, and that molecular oxygen remains a useful biosignature for certain types of Earth-like extrasolar planets.

The study, “Abiotic O2 Levels on Planets around F, G, K, and M Stars: Effects of Lightning-produced Catalysts in Eliminating Oxygen False Positives,” was published in The Astrophysical Journal. The work was supported through NASA’s Habitable Worlds Program and the Nexus for Exoplanet System Science (NExSS). The NASA Astrobiology Program provides resources for Habitable Worlds and other Research and Analysis programs within the NASA Science Mission Directorate (SMD) that solicit proposals relevant to astrobiology research. NExSS is a NASA research coordination network supported in part by the NASA Astrobiology Program. This program element is shared between NASA’s Planetary Science Division (PSD) and the Astrophysics Division.