University study helps limit search for life outside earth

James Pollard, Assistant Campus Editor

In this past summer’s blockbuster “Men in Black: International,” “Agent M” — 23 years removed from an alien encounter — joins the MiB after being rejected from the FBI and CIA due to her delusions concerning alien life.

But determining whether or not life exists outside of earth may have gotten easier.

A new Northwestern study will help astronomers limit their search for potential life in outer space, a Nov. 11 University news release announced. Howard Chen, a Ph.D. candidate in Northwestern’s Climate Change Research Group and a NASA future investigator, was the study’s first author. Earth and planetary sciences Prof. Daniel Horton was the senior author of the study, published online in the Astrophysical Journal on Nov. 14.

“‘Are we alone?’ is one of the biggest unanswered questions,” Chen said in the release. “If we can predict which planets are most likely to host life, then we might get that much closer to answering it within our lifetimes.”

The research team is the first to combine 3D climate modeling with atmospheric chemistry to explore the habitability of planets around M dwarf stars, the release said. By considering the star’s radiation and the planet’s rotation rate, the researchers have redefined the conditions that make a planet habitable.

The Northwestern team collaborated with researchers at the University of Colorado Boulder, NASA’s Virtual Planet Laboratory and the Massachusetts Institute of Technology. They found that planets orbiting stars that emit a lot of ultraviolet radiation lose significant water to vaporization. Planets around inactive or quiet stars are more likely to maintain liquid water that is life-sustaining, the study found.

The study also determined that planets with thin ozone layers, which otherwise have habitable surface temperatures, receive dangerous UV levels — hazardous for complex surface life.

M dwarf planets are the frontrunners in this search because they are numerous and easier to find and investigate.

“For most of human history, the question of whether or not life exists elsewhere has belonged only within the philosophical realm,” Chen said in the release. “It’s only in recent years that we have had the modeling tools and observational technology to address this question.”

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Twitter: @pamesjollard

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