ASU researchers look at the possibility of life outside Earth

Biosignatures like the organization of Earth's atmosphere could contribute to life on other planets

ASU researchers have come together to figure out what we know about life outside of Earth. 

In the article “Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life,” one of two articles contributed by ASU scientists and the first of five total for a special issue of the scientific journal Astrobiology, ASU researchers review the past 20 years of study on biosignatures that sets the stage for how people can begin to look for and recognize the signs of life on other planets.

Theresa Fisher, a doctoral student in the School of Earth and Space Exploration, said that most of the work they completed was focused on trying to figure out what biosignatures of a planet's atmosphere might indicate the presence of life.

“Most oxygen here on Earth is produced by plant life, but there was also discussion about the fact that you can't always necessarily trust that there are ways you can get a lot of oxygen that have absolutely nothing to do with light chemistry involving ultraviolet radiation from a star,” Fisher said. “We also talked about sort of more exotic ways of detecting life; everything from looking for spectral signatures of chlorophyll or other biological pigments, looking at differences over the course of a year that suggests some sort of seasonal, biological pattern.”

Fisher said that a large portion of this whole project was to think about future projects, missions, a new generation of space telescopes or new observing campaigns for ground based telescopes. They asked themselves, what are researchers looking for? What should researchers be keeping an eye out for? 

Oceanographer Hilairy Hartnett, an associate professor in the School of Earth and Space Exploration and in the School of Molecular Sciences, said in an email that the article was a product of a workshop on exoplanet biosignatures.

This workshop is related to a large NASA initiative to study exoplanets, planets around other stars.

She was one of the coordinators of the project and helped to provide information about oxygen biosignatures. 

“My background is in oceanography and biogeochemistry, so I study the effects that biological processes have on ecosystems and their chemical environments,” Hartnett said. “I am interested in large, planetary scale processes and how they can inform us about whether planets can support life and how we would recognize a living planet vs. a non-living planet.”

Hartnett said that searching for life beyond Earth has been a fundamental question ever since humans realized that the Earth was part of a larger universe. 

“Now that we know there are planets around other stars, it is not surprising that we wonder if those planets are like ours,” Hartnett said. “Is there anyone living on those planets? Even if that ‘anyone’ is microbes.”

Hartnett said that, for the foreseeable future, the search for life outside Earth will be done with large telescopes and will involve looking at the atmospheres of those exoplanets. 

Fisher said something that they’ve only recently started looking into are the properties of different atmospheres, but from the very preliminary research they've done.

“There was a group of network theorists for all the major planetary atmospheres in our own solar system,” Fisher said. “What they noticed is that the mathematical properties and even just the general shape of the network for Earth looks very, very different from all the other atmospheres in the solar system.”

Fisher said that other planets’ atmospheres tend to be random. 

“There didn't seem to be much pattern to them, like balls of Spaghetti, basically,” Fisher said. “Earth's atmosphere looks organized. (The atmosphere) is discreetly dividable into sub units that would connect them to larger units.”

Fisher said that we don’t know if Earth’s organized atmosphere is due to the presence of life. She said it could be, or it could just be a fluke. 

Fisher said that scientists suspect that this organization is significant and could potentially detect life on other planets.

Hartnett said that researchers need to understand the gases in atmospheres and how they are produced in order to know if the presence of life affects atmospheres.

“This is really exciting science and this type of work will inform us not only about other planets but also about processes at work here on our own planet,” Hartnett said.

Reach the reporter at or follow @jessiemy94 on Twitter. 

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