Scientists have spent decades searching for extraterrestrial life by looking for specific signals from individual planets. However, a new study argues that this method could overlook a larger pattern.
A team led by Harrison B. Smith at the Earth-Life Science Institute in Tokyo and Lana Sinapayen at the National Institute for Basic Biology has introduced a new way to search for life beyond Earth. Rather than zeroing in on individual planets, their approach looks for patterns that emerge across entire groups of worlds.
Their findings, recently published in The Astrophysical Journal, introduce the concept of an “agnostic biosignature,” which could influence how scientists select targets in the search for extraterrestrial life moving forward.
The Problem With Looking for Specific Signs
Most searches for alien life still rely on two main tactics. Scientists either look for biosignatures like oxygen or methane in a planet’s atmosphere that could hint at life, or they hunt for technosignatures, which are signs of technology. However, both methods have their pitfalls: biosignatures can be produced by non-living chemistry, and technosignatures require us to guess how alien civilizations might behave. The agnostic biosignature approach aims to sidestep both of these challenges.
“Realistically, there are just a few locations to search for alien life within the solar system,” the researchers write. “Outside the solar system, opportunities are nearly unlimited, but there’s a catch: it is difficult to attribute, with certainty, features of exoplanets to extraterrestrial life.”
Life Leaves Footprints Across Many Worlds
This method relies on two main ideas. One is that life can spread from planet to planet through a process called panspermia. The other is that the presence of life modifies planets in ways that create detectable correlations between a planet’s properties and its location. If both are true, then life would leave patterns across many planets, not just one.
To test their theory, the researchers built a computer simulation to see how life might spread through star systems and change planets. They found that life created measurable links between a planet’s location and its physical characteristics. These patterns appeared even when no single planet showed a clear biosignature.
This approach does not focus on finding planets similar to Earth. Instead, it searches for groups of planets that are more similar to each other than would be expected by chance and that are located near each other in space. According to the researchers, this similarity could be a sign of life influencing multiple planets.
Guiding Telescopes in the Right Direction
In addition to detecting signs of life, the team developed a way to identify which planets are most promising for further study. By grouping planets by their observable features and positions in space, the method highlights clusters of planets that are more likely to have been influenced by biological processes.
This strategy favors accuracy over completeness. Although it may overlook some planets that harbor life, it greatly reduces the likelihood of false positives. This trade-off becomes critical when telescope time is limited, and each follow-up observation carries a cost.
“By focusing on how life spreads and interacts with environments, we can search for it without needing a perfect definition or a single definitive signal,” Smith said. Sinapayen added: “Even if life elsewhere is fundamentally different from life on Earth, its large-scale effects, such as spreading and modifying planets, may still leave detectable traces. That’s what makes this approach compelling.”
Next Steps
Right now, the study uses computer simulations instead of real data from planets, and the researchers admit this is a limitation. To improve the method, scientists need to learn more about the natural differences between lifeless planets. This will help them identify changes caused by the presence of life. Future research should also use more realistic models of how galaxies and planetary systems form and change.
New telescopes will soon be able to examine thousands of exoplanets simultaneously, providing scientists with ample datasets they need for this method. If alien life has been changing planets across the galaxy, the proof might not be a signal from just one planet, but a pattern seen across several worlds.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.