Astronomers identify trick to root out false-positives in the search for life

A new study hopes to cut down on false positive readings in the search for ET. It highlights two scenarios in which the detection of oxygen (O2) in the atmosphere of a distant exoplanet would not represent the presence of extraterrestrial life.

One of the methodscurrently in use by astronomers engaged in the hunt forextraterrestrial life is to analyze the atmospheres of distantexoplanets searching for O₂, a gas which on Earthis created largely via photosynthesis in plants and algae, and is synonymous with the existence of life.

So, how do astronomersdetermine whether an exoplanet has O₂ in its atmosphere?Scientists are able to observe exoplanets as they pass in front oftheir parent stars, taking the opportunity to analyze the spectralfeatures of the light as it glances through the planet's atmosphere. From this, astronomersare able to break down the composition of the atmosphere, and infercertain characteristics about their quarry, including theinterpretation of significant levels of O₂ as a potentialindicator for life.

However, a new studyhas outlined two cases in which the detection of O₂ in theatmosphere of a distant planet would provide a false positiveindicator in the search for life. In both scenarios, the O₂present in an exoplanet's atmosphere would exist as a result ofabiotical production.

One such scenario wouldsee ultraviolet light from a common star smaller than our Sun strikean exoplanet's atmosphere, breaking down carbon dioxide (CO₂)to free O₂ particles. The team ran computer models tosimulate the interaction and discovered that alongside producing O₂,that the CO₂split would also produce largequantities of carbon monoxide (CO)

Therefore, if oxygen isdetected alongside a strong presence of CO₂ and CO,it could represent a false positive. A low-mass star is once againthe catalyst for another potential false positive indicator in thesearch for life wherein light from the star could work to break downatmospheric water.

This creates vastquantities of O₂which may collide with each other to create short lived O₄molecules. The detection of O₂alongside O₄could serve as another indicator for a false positive, allowingastronomers to save valuable time by viewing more promising targets.

Research such as thiswill provide a valuable framework in the search for life, as it isaided by the next generation of scientific instruments, includingNASA's greatly anticipated James Webb Space Telescope.

A paper on the studyhas been published in The Astrophysical Journal.

Source: University of Washington