Researchers Use 3D Climate Modeling to Estimate Planet Habitability

This artist’s impression shows the planet orbiting the Sun-like star HD 85512 in the southern constellation of Vela (The Sail). This planet is one of sixteen super-Earths discovered by the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory. This planet is about 3.6 times as massive as the Earth lis at the edge of the habitable zone around the star, where liquid water, and perhaps even life, could potentially exist.

NASA missions like Kepler and the Transiting Exoplanet Survey Satellite (TESS) have revealed just how many planets there are in the universe. Simply knowing that planets exist doesn’t tell us if there’s anyone living there. When astronomers suggest an exoplanet could be habitable, that’s a very rough estimate. A new study is the first to use 3D climate modeling to help nail down which exoplanets could support life. 

Red dwarf stars (sometimes called M dwarfs) are the most common type in the galaxy — there’s one right next door called Proxima Centauri. You might remember hearing a lot about Proxima Centauri in the last few years because there’s strong evidence for an Earth-like exoplanet there. Indeed, scientists think red dwarf stars host a plethora of exoplanets. While they’re smaller and cooler than our sun, they’re very long-lived and exoplanets could host liquid water if they orbit close enough. 

The new study from Northwestern University researchers combined 3D climate models with photochemistry and atmospheric chemistry, a first for exoplanet research. This research didn’t involve observing exoplanets but rather focused on creating a model that more accurately calculates the effects of solar radiation. The team believes this simulation provides a fuller picture of conditions on the surface of exoplanets, allowing astronomers to prioritize observations on the most likely targets. 

eso exoplanet

This artist’s impression shows the planet Proxima b orbiting in the Goldilocks zone around the red dwarf star Proxima Centauri, the closest star to the Solar System.

According to the researchers, 3D photochemistry hasn’t been used in exoplanet research because it’s so computationally expensive. Taking the time to do it, however, shows that such techniques can be vital to estimating the heating and cooling effects of solar radiation. Knowing how solar radiation interacts with the gases in a planet’s atmosphere can help differentiate between Earth-like planets and acidic hellscapes like Venus. For example, a planet might be inside the habitable zone of a star, but its thin ozone layer could mean too much ultraviolet radiation on the surface. The simulations also show that planets orbiting active stars are susceptible to losing significant water through vaporization. Without liquid water, life as we know it is impossible. 

This research could help guide future studies of distant planets, particularly when the James Webb Space Telescope comes online in a few years. That instrument will have vastly increased sensitivity compared with Hubble, allowing it to detect water vapor and ozone in planetary atmospheres. Astronomers just need to know which planets are the most likely homes to alien life.

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