When you buy through links on our articles, Future and its syndication partners may earn a commission.What clues do scientists look for to see if an exoplanet is habitable?. | Credit: Pixabay.comThis article was originally published at The Conversation. The publication contributed the article to Space.com’s Expert Voices: Op-Ed & Insights. When astronomers search for planets that could host liquid water on their surface, they start by looking at a star’s habitable zone. Water is a key ingredient for life, and on a planet too close to its star, water on its surface may “boil”; too far, and it could freeze. This zone marks the region in between.AdvertisementAdvertisementAdvertisementAdvertisementBut being in this sweet spot doesn’t automatically mean a planet is hospitable to life. Other factors, like whether a planet is geologically active or has processes that regulate gases in its atmosphere, play a role.The habitable zone provides a useful guide to search for signs of life on exoplanets – planets outside our solar system orbiting other stars. But what’s in these planets’ atmospheres holds the next clue about whether liquid water — and possibly life — exists beyond Earth.On Earth, the greenhouse effect, caused by gases like carbon dioxide and water vapor, keeps the planet warm enough for liquid water and life as we know it. Without an atmosphere, Earth’s surface temperature would average around zero degrees Fahrenheit (minus 18 degrees Celsius), far below the freezing point of water.The boundaries of the habitable zone are defined by how much of a “greenhouse effect” is necessary to maintain the surface temperatures that allow for liquid water to persist. It’s a balance between sunlight and atmospheric warming.AdvertisementAdvertisementAdvertisementAdvertisementMany planetary scientists, including me, are seeking to understand if the processes responsible for regulating Earth’s climate are operating on other habitable zone worlds. We use what we know about Earth’s geology and climate to predict how these processes might appear elsewhere, which is where my geoscience expertise comes in.An artist’s representation of the ‘habitable zone,’ the range of orbits around a star where liquid water may exist on the surface of a planet. | Credit: Erik A. PetiguraWhy the habitable zone?The habitable zone is a simple and p …
