“Project Hail Mary,” the movie adaptation to Andy Weir’s 2021 novel about a science teacher attempting to save the Earth from sun-eating microbes, was released in March 2026 to stellar ratings from critics and audiences alike. The movie explores a few unique forms that extraterrestrial life could take, from space microorganisms that produce both infrared light and an unfathomable amount of energy, to rocklike aliens that live under crushing pressure and breathe ammonia.
Over the past decade, scientists have come up with a variety of frameworks to guide their search for life in the universe. While it’s most convenient to start looking for life using the knowledge that biologists have about life on Earth, scientists have also begun integrating broader conceptions of life, including life that perhaps evolved in different chemical environments.
To expand on the idea that life out in space might look nothing like life on Earth, here are five articles The Conversation U.S. rounded up from our archives, and written by astronomers and astrobiologists.
1. Why base the search on life on Earth?
Astronomers participating in the Search for Extraterrestrial Intelligence typically start by identifying potentially habitable planets. And to do that, they look for what sustains life on Earth: water.
Planets that are close enough to their Sun that liquid water wouldn’t freeze, but far enough away that it wouldn’t evaporate, fall into what’s called the Goldilocks Zone. But why base the search on water, which complex life on Earth uses to survive, if an extraterrestrial life-form might use different chemistry?
Cole Mathis, a physicist and astrobiologist at Arizona State University who studies complex adaptive systems, explained that out of convenience, astronomers start by looking for signals similar to those produced by life on Earth.
Detecting chemical signatures using the instruments on telescopes is tricky – it’s like playing hide-and-seek, but you’re outside the house and can only peer in through the window. You might as well start by ruling out the easy and more obvious hiding spots.
By measuring the depth of the dip in brightness and knowing the size of the star, scientists can determine the size or radius of the planet.
NASA Ames
Missions to Mars have looked for signs of photosynthesis – the process by which plants take in energy – and telescopes peering deep into space look for oxygen, which organisms on Earth release into the atmosphere.
“Most astronomers and astrobiologists know that if we only look for life that’s like Earth life, we might miss the signs of aliens that are really different,” Mathis wrote. “But honestly, we’ve never detected aliens before, so it’s hard to know where to start. When you don’t know what to do, starting somewhere is usually better than…
