Celestial carbon monoxide detectors could warn us of extraterrestrial life

Artist's illustration to demonstrate the concept that carbon monoxide detectors could alert us to extraterrestrial life
© NASA, ESA, G. Bacon (STScI)

Carbon monoxide detectors could alert us to extraterrestrial life, according to a research team led by the University of California Riverside.

Astronomers have generally assumed that the build up of carbon monoxide in a planet’s atmosphere would be a sign of lifelessness. However, the new research argues that celestial carbon monoxide detectors could actually alert us to simple extraterrestrial life forms.

Scenarios in which carbon monoxide accumulates

The team used computer models of chemistry in the biosphere and atmosphere to identify two scenarios in which carbon monoxide accumulates in living planets’ atmospheres.

The first scenario is that of our own planet’s past. The team’s models showed that the ancient version of inhabited Earth could maintain carbon monoxide levels of roughly 100 parts per million (ppm), which is several orders of magnitude greater the parts-per-billion traces of the gas in the atmosphere today.

A second scenario is that the photochemistry around red dwarf stars like Proxima Centauri, the star nearest our sun at 4.2 light years away. The team predicted that if a planet around such a star was inhabited and rich in oxygen, then there would be a high abundance of carbon monoxide, anything from hundreds of ppm to several percent.

The search for life in the universe

One of the study’s co-authors, and a professor of biogeochemistry in the department of Earth Science at UCR, Timothy Lyons, said: “That means we could expect high carbon monoxide abundances in the atmospheres of inhabited but oxygen-poor exoplanets orbiting stars like our own sun. This is a perfect example of our team’s mission to use the Earth’s past as a guide in the search for life elsewhere in the universe.”

Edward Schwieterman, the study’s lead author and a NASA Postdoctoral Program fellow in UCR’s Department of Earth Sciences, added: “With the launch of the James Webb Space Telescope two years from now, astronomers will be able to analyze the atmospheres of some rocky exoplanets. It would be a shame to overlook an inhabited world because we did not consider all the possibilities.”

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