A new John Hopkins University study has shown that the presence of oxygen in a planet’s atmosphere is not a sure sign that there is life on other planets.
In the search for life in solar systems, researchers have accepted the observation of oxygen as an indication of the presence of life on other planets. This new study recommends a reconsideration of that rule. The findings have been published in the journal ACS Earth and Space Chemistry.
The researchers simulated the atmospheres of planets beyond the solar system in the lab, and successful created organic compounds and oxygen that were absent of life, showing that oxygen does not necessarily indicate life. The researchers tested nine different gas mixtures, based on predictions for super-Earth and mini-Neptune type exoplanet atmospheres.
The Earth’s atmosphere
Oxygen makes up 20 percent of the Earth’s atmosphere. It is considered one of the most robust biosignature gases in Earth’s atmosphere.
In the search for life beyond the Earth’s solar system, however, different energy sources initiate chemical reactions and how they can create biosignatures such as oxygen.
Previously other researchers have ran photochemical models on computers to predict what exoplanet atmospheres might be able to create.
Life on other planets
Chao He, assistant research scientist in the Johns Hopkins University Department of Earth and Planetary Sciences and the study’s first author, said: “Our experiments produced oxygen and organic molecules that could serve as the building blocks of life in the lab, proving that the presence of both doesn’t definitively indicate life. Researchers need to more carefully consider how these molecules are produced.”
Explaining further, He added: “People used to suggest that oxygen and organics being present together indicates life, but we produced them abiotically in multiple simulations. This suggests that even the co-presence of commonly accepted biosignatures could be a false positive for life.”