Oxygen might not lead us to aliens after all. A new study shows us why we may want to rethink how we search for extraterrestrial life.

Pedro_P

A new study published inACS Earth and Space Chemistrysuggests the presence of atmospheric oxygen on another planet is far from a sure sign.
NASA, ESA, G. Illingworth (UCO/Lick Observatory and the University of California, Santa Cruz), R. Bouwens (UCO/Lick Observatory and Leiden University) and the HUDF09 Team
▼ The huge bloom in exoplanet  discoveriesover the last decade gives us more and more hope we’ll soon find life on another world. While water remains the most important sign that alien life is possible, scientists look for many other chemical elements and compounds that could bolster the ability for extraterrestrial life to evolve and sustain itself elsewhere. Oxygen is obviously one such “biosignature,” given how important it is to complex life here on this planet.
But maybe we’re putting too much stock in the air we breathe. A new study published in ACS Earth and  Space Chemistrysuggests the presence of atmospheric oxygen on another planet is far from a sure sign.
“The presence of oxygen in Earth’s atmosphere, in significant quantities, is due to the presence of life,” says Nikole Lewis, an exoplanet scientist from Cornell University and a coauthor of the new study. While life could certainly exist without significant access to oxygen, “most of current thinking on how to detect life on other planets focuses on finding planets with atmospheres very similar to Earth’s,” she says.
However, before knowing whether a gas or a combination of gases indicates life, “we have to fully understand the chemistry happening on a planet,” says Chao He, a researcher at Johns Hopkins University and the lead author of the new paper. “Our study provides some insight into the atmospheric chemistry” and suggests certain processes could easily produce oxygen sans biology. Scientists might need to consider that oxygen could be a false flag for signs of alien life.
Naturally, this is not an easy question to investigate. He and his colleagues took advantage of Johns Hopkins’ special Planetary HAZE Research, or PHAZER: an experimental chamber that can simulate a broad range different atmospheric chemistry conditions, from the frigid surface of Pluto to the incredibly hot high altitudes of Venus. The idea is to expose precisely mixed gases to a high energy source (plasma or UV light, both of which can be emitted from a star) to see if hazes (small particles produced by photochemical reactions) will form, and if this will alter the atmosphere’s chemistry itself.
“The idea is to be able to not just simulate chemical processes happening in these atmospheres, but also vary them in a systematic way to try to understand what processes actually dominate the things we are actually able to observe with spacecraft and telescopes,” says Sarah Hörst, a professor of planetary science from Johns Hopkins University and a coauthor of the new paper.
He and his team ended up testing nine different gas mixtures that simulated predicted atmospheric chemistries on super-Earth and  (▪ ▪ ▪)

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