What if we don't find alien life in the Universe? That might be OK, too

Scientists continue designing new tools to scan the skies for any sign of life on worlds light-years away. But what if every signal we check comes back empty? Could a complete lack of discoveries teach us about the rarity of life another planets and the galaxy?

This question guided the efforts of Dr. Daniel Angerhausen, a Physicist in Professor Sascha Quanz’s Exoplanets and Habitability Group at ETH Zurich and a SETI Institute affiliate.

He and collaborators recently applied a statistical lens to this possibility and uncovered surprising insights.

“No life” can still teach us about life

Their latest analysis looked at how a full lack of biosignature signals could still reveal whether life is widespread.

In a paper using Bayesian statistics, the team explains that checking around 40 to 80 exoplanet targets with no detections could indicate if under 10 to 20% of similar planets host living processes.

They highlight that every measurement carries errors, so researchers must handle those uncertainties or risk jumping to the wrong interpretation.

The group worked through Frequentist methods too, finding that both approaches can align when enough worlds are investigated.

Planets may hide life or give false clues

False negatives can creep in if an atmosphere masks signs of life. Improper target selection or gaps in data could also distort results.

“It’s not just about how many planets we observe – it’s about asking the right questions and how confident we can be in seeing or not seeing what we’re searching for,” says Angerhausen. He emphasizes the need for prudence. 

“If we’re not careful and are overconfident in our abilities to identify life, even a large survey could lead to misleading results,” says Angerhausen.

This caution shapes the planning for new instruments that aim to spot subtle atmospheric patterns.

More planets give better answers

Tools like the Large Interferometer for Exoplanets (LIFE) are on the horizon to inspect planetary atmospheres and search for water or oxygen.

Experts suggest that a robust sample is essential so that random outliers don’t skew the entire picture.

“In applied science, Bayesian and Frequentist statistics are sometimes interpreted as two competing schools of thought,” says Emily Garvin, a PhD student in Quanz’s group, underscoring how the choice of statistical model can shift the conclusion. 

“Slight variations in a survey’s scientific goals may require different statistical methods to provide a reliable and precise answer,” says Garvin.

She adds that comparing both methods helps validate assumptions at each step.

Clear questions help find signs of life on planets

One of the key takeaways from the study is that not all questions carry the same weight. Asking “How many planets have life?” is too vague to lead to reliable answers.

Instead, the researchers recommend focusing on specific, measurable traits.

For example, asking how many rocky planets in the habitable zone show traces of water vapor, oxygen, or methane helps isolate variables and reduce confusion.

Early assumptions can skew final results

The team also explored how assumptions made before data collection – called priors in Bayesian terms – can shape final results.

This matters when earlier studies or models already lean optimistic or pessimistic.

For missions like LIFE and NASA’s Habitable Worlds Observatory, the influence of these assumptions is expected to be small when surveying dozens of planets.

That’s because larger samples can help drown out personal bias and strengthen overall conclusions.

Clear rules help future space missions

Clear definitions are vital so that researchers limit confusion when they classify planets. Even advanced instruments need rigorous protocols to handle noise or incomplete data.

“A single positive detection would change everything,” says Angerhausen. These discussions also hint at how important it is to plan for rare success. 

Where this leaves us

Questions about life’s scarcity influence how we invest in telescopes and data processing. The team’s work may guide future surveys as they measure water, methane, and more on new targets.

Finding no signals of life on a planet doesn’t mean we learn nothing. It shines a light on how empty data can still sharpen our sense of what else might be out there.

Scientists continue to refine ways to decode faraway environments. They aim to separate misleading noise from real clues, inching closer to answering whether we are alone.

The study is published in The Astronomical Journal.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–