In the late 2000s, Sarah Stewart Johnson found herself atop Mauna Kea in Hawaii, an experience that stirred her imagination about life beyond Earth. The stark, arid landscape contrasted sharply with her lush Kentucky upbringing. While exploring, she unexpectedly encountered a small fern growing from volcanic rock, which led her to ponder the resilience of life. Johnson's thoughts shifted beyond earthly concerns to the possibility of alien life, prompting her to consider how life could exist in forms unfamiliar to us. "This trip ignited my curiosity about searching the universe for life," she noted.

Subsequently, Johnson became a prominent researcher, delving into genetic methodologies to detect extraterrestrial life during her time as a post-doctoral astronomer at Harvard University. She became fascinated by the future Alien Genome Project but also questioned whether alien organisms would rely on DNA or RNA as we do. What if their life forms employed entirely different biochemical mechanisms?

To express her groundbreaking ideas, Johnson began writing for scientific journals, ultimately culminating in her 2020 science fiction novel, The Mermaids of Mars. In it, she posits that extraterrestrial life could differ fundamentally from Earth’s life forms. "Even seemingly familiar places like Mars can surprise us," she remarked. "What if those surprises are indicative of life?"

If Johnson's hypothesis holds true, the prevailing methods for searching for life—predicated on our understanding of biology—might fall short. "There's an old saying: if you lose your keys, you first look where you know," she explained, now an associate professor at Georgetown University. Most space missions focus on detecting chemical "biosignatures," which are indicative of life as we know it. However, if we limit ourselves to familiar chemical signatures, we risk overlooking entirely different forms of life. "How do we overcome this bias?" Johnson asked. She advocates for a more inclusive scientific approach that considers alternative biochemistries, coining the term "LAWDKI" to encapsulate life as we don’t yet know it.

Now, as the lead investigator for NASA's Agnostic Biosignature Laboratory (LAB), Johnson is at the forefront of this research. LAB does not rely on a specific biochemical framework, aiming instead to identify markers of biological significance, such as complex molecular structures that suggest biological activity. This initiative could potentially address humanity’s enduring question: Are we alone in the universe?

A significant challenge in studying life lies in the lack of consensus on its definition and origins. In 2011, geneticist Edward Trifonov proposed a unifying concept, summarizing over 100 definitions of life into one: "self-replication and variation." Similarly, NASA has defined life as an autonomous chemical process capable of Darwinian evolution.

These definitions do not necessitate a unique chemistry. On Earth, life is based on DNA, a double-stranded molecule comprised of sugars and phosphates, with bases that encode genetic information. However, if life elsewhere does not conform to these biochemical norms, it may embody something entirely different.

Researchers speculate that all life requires a method to generate and evolve biological instructions, but extraterrestrial life might employ alternative biochemical systems. For instance, Northwestern University researchers developed spherical nucleic acids (SNA) in the 1990s. NASA's 2019 studies demonstrated that synthetic DNA could be constructed using both traditional and novel bases. If we can engineer diverse genetic systems in a lab, then surely the cosmos harbors even more imaginative life forms.

Leroy Cronin from the University of Glasgow believes it's time to shift our focus away from Earth-centric definitions of life. "Biology is unique to our planet," he argues, suggesting that we should search for "star life" instead.

Stuart Bartlett of the California Institute of Technology echoes this sentiment, suggesting that the quest for different life forms is actually a search for "lyfe," a broader term that encompasses any system meeting the four conditions of life. This definition emphasizes energy usage, self-sustaining chemical reactions, homeostasis, and information processing.

The distinction between "life" and "lyfe" highlights the necessity for open-mindedness in our explorations. As researchers continue to seek life beyond Earth, they often fall back on familiar benchmarks, such as oxygen in exoplanet atmospheres. This bias might lead to misinterpretations of potential life indicators in other worlds, where conditions are vastly different.

Even when scientists stumble upon previously unknown organisms, they often frame their discoveries within existing knowledge. For example, when Antonie van Leeuwenhoek observed single-celled life through a microscope in the 17th century, he labeled them "animalcules," despite their stark differences from multicellular organisms.

Heather Graham, deputy director of research at NASA's Goddard Space Flight Center and LAB collaborator, views these historical discoveries as part of the ongoing search for LAWDKI. In 2016, Johnson joined forces with like-minded researchers, exploring how complexity could serve as an indicator of biological presence. During a NASA conference, they proposed developing a tool to measure molecular interactions, recognizing that complex systems are more likely to exhibit distinctive patterns than random chemical assemblages.

Despite initial setbacks, NASA's subsequent support allowed them to collaborate across disciplines. They aim to deploy instruments capable of detecting life in extreme environments, such as the icy moons of Europa and Enceladus. "As we target these bizarre locations, we must be prepared for life forms that defy our expectations," Johnson stated.

This collaborative effort has since evolved into the LAB project, which aims to investigate how various factors, like surface tension and energy transfer, might reveal unknown forms of life. Fieldwork includes visits to Kidd Creek Mine in Canada, where scientists study geological formations that may mimic conditions on potential ocean worlds.

At Kidd Creek, they will differentiate between minerals formed through crystallization and those that may arise from biological activity. Identifying such distinctions could lead to new insights regarding the geological conditions conducive to life.

Johnson's team is applying genetic techniques to explore cellular binding sites, seeking to understand the interactions that define living organisms. Their work aims to distinguish between living and non-living systems based on energy utilization and chemical imbalances.

The LAB research team is also examining chemical fractionation, which describes how life selectively incorporates elements and isotopes. This understanding could guide future explorations, allowing scientists to identify environments where life might thrive based on elemental patterns.

As the search for extraterrestrial life continues, the journey remains fraught with challenges. Johnson and her colleagues strive to broaden our understanding of what constitutes life, paving the way for potentially groundbreaking discoveries in the realms of astrobiology and beyond.