Sara Walker
· ProfessorVerifiedArizona State University · School of Complex Adaptive Systems
Active 2003–2026
About
Professor Sara Walker is an astrobiologist and theoretical physicist with research interests in the origins of life, artificial life, and life detection on other worlds. Since joining Arizona State University in 2013, she has developed a highly interdisciplinary research program aimed at understanding the origin of life from multiple perspectives. She has mentored numerous early career scientists and leads one of the largest theory groups in origins of life and astrobiology internationally. Her team's major contributions include theoretical advances in astrobiology, developing new approaches to understanding universal features of life, detecting alien life, and designing synthetic life. At ASU, she serves as Deputy Director of the Beyond Center for Fundamental Concepts in Science and as Associate Director of the ASU-Santa Fe Institute Center for Biosocial Complex Systems. She holds joint appointments in the School of Earth and Space Exploration and the School of Complex Adaptive Systems, and is a member of the External Faculty at the Santa Fe Institute. Her work includes leading a NASA Indisciplinary Consortia for Astrobiology Research project focused on planetary systems biochemistry, which provides tools for identifying signs of life. She has been recognized with the Stanley Miller Early Career Award for her leadership in life detection and origins of life research. Additionally, she contributes to tech transfer initiatives, including projects aimed at developing non-addictive opioid drugs, and actively participates in various scientific steering committees and boards. She is dedicated to public engagement, reaching audiences through lectures, podcasts, and other activities.
Research topics
- Computer Science
- Physics
- Artificial Intelligence
- Astrobiology
- Astronomy
- Philosophy
- Computer Security
- Epistemology
- Data Mining
- Evolutionary biology
- Cognitive science
- Data science
- Geography
- Engineering
- Psychology
- Theoretical physics
- Paleontology
- Computational biology
- Geology
- Ecology
- Biology
- Environmental science
Selected publications
Zenodo (CERN European Organization for Nuclear Research) · 2026-01-26
otherOpen accessSenior authorFull Changelog: https://github.com/ELIFE-ASU/CBRdb/compare/v1.8.0...v1.9.0
arXiv (Cornell University) · 2026-01-10
preprintOpen accessExecutive Summary: The Habitable Worlds Observatory (HWO) is the first astrophysics flagship mission with a key cross-divisional astrobiology science goal of searching for signs of life on rocky planets beyond our solar system. The Living Worlds Working Group under the Science, Technology, and Architecture Review Team (START) was charged with investigating how HWO could characterize potentially habitable exoplanets orbiting stars in the solar neighborhood, search for signs of life, and interpret potential biosignatures within a false positive and false negative framework. In particular, we focused on (1) identifying biosignatures that have spectral features in the UV-Vis-NIR wavelength range and defining their measurement requirements, (2) determining additional information needed from the planet and planet system to interpret biosignatures and assess the likelihood of false positives, and (3) assembling current knowledge of likely HWO target stars and identify which properties of host stars and systems are most critical to know in advance of HWO. The Living Worlds atmospheric biosignatures science case is considered one of the key drivers in the design of the observatory. An additional 10 astrobiology science cases were developed that collectively revealed key research gaps and needs required to fully explore the observatory parameter space and perform science return analyses. Investment in these research gaps will require coordination across the Science Mission Directorate and fall under the purview of the new Division-spanning astrobiology strategy.
Metrology of Complexity and Implications for the Study of the Emergence of Life
Open MIND · 2026-02-20
preprint1st authorCorrespondingOne of the longest standing open problems in science is how life arises from non-living matter. If it is possible to measure this transition in the lab, then it might be possible to understand the physical mechanisms by which the emergence of life occurs, which so far have evaded scientific understanding. A significant hurdle is the lack of standards or a framework for cross comparison across different experimental contexts and planetary environments. In this essay, I review current challenges in experimental approaches to origin of life chemistry, focusing on those associated with quantifying experimental selectivity versus de novo generation of molecular complexity, and I highlight new methods using molecular assembly theory to measure molecular complexity. This metrology-centered approach can enable rigorous testing of hypotheses about the cascade of major transitions in molecular order marking the emergence of life, while potentially bridging traditional divides between metabolism-first and genetics-first scenarios. Grounding the study of life's origins in measurable complexity has significant implications for the search for life beyond Earth, suggesting paths toward theory-driven detection of biological complexity in diverse planetary contexts. As the field moves forward, standardized measurements of molecular complexity may help unify currently disparate approaches to understanding how matter transforms to life. Much remains to be done in this exciting frontier.
ArXiv.org · 2026-01-10
articleOpen accessExecutive Summary: The Habitable Worlds Observatory (HWO) is the first astrophysics flagship mission with a key cross-divisional astrobiology science goal of searching for signs of life on rocky planets beyond our solar system. The Living Worlds Working Group under the Science, Technology, and Architecture Review Team (START) was charged with investigating how HWO could characterize potentially habitable exoplanets orbiting stars in the solar neighborhood, search for signs of life, and interpret potential biosignatures within a false positive and false negative framework. In particular, we focused on (1) identifying biosignatures that have spectral features in the UV-Vis-NIR wavelength range and defining their measurement requirements, (2) determining additional information needed from the planet and planet system to interpret biosignatures and assess the likelihood of false positives, and (3) assembling current knowledge of likely HWO target stars and identify which properties of host stars and systems are most critical to know in advance of HWO. The Living Worlds atmospheric biosignatures science case is considered one of the key drivers in the design of the observatory. An additional 10 astrobiology science cases were developed that collectively revealed key research gaps and needs required to fully explore the observatory parameter space and perform science return analyses. Investment in these research gaps will require coordination across the Science Mission Directorate and fall under the purview of the new Division-spanning astrobiology strategy.
arXiv (Cornell University) · 2026-01-02
preprintOpen accessSenior authorAssembly theory (AT) introduces causation as a material property and establishes a metrology for objects produced by evolution and selection. The physical scale of causation is quantified by the assembly index, defined as the minimum number of recursive steps necessary to make an object. Observing countable copies of high assembly index objects indicates a mechanism producing them is persistent, such that the object's environment constructs a memory that traps causation within a contingent chain. Copy number and assembly index together underlie a standardized metrology for detecting causation (assembly index) and contingency (copy number). These allow a precise definition of an assembly threshold that demarcates life (and its derivative agential, intelligent, and technological forms and artifacts) as structures with persistent copies in regimes of deep causal possibility. In introducing a fundamental concept of material causation to quantify and measure life, AT represents a departure from prior theories of causation, such as interventional ones, which have so far proven incompatible with fundamental physics. We discuss how AT's concept of causation provides the foundation for a theory of physics that allows precise and testable concept of "life", and in which novelty, contingency and the potential for open-endedness are fundamental, and determinism is emergent from selection along assembled lineages.
arXiv (Cornell University) · 2026-01-14
preprintOpen accessThe discovery of a biosphere on another planet would transform how we view ourselves, and our planet Earth, in relation to the rest of the cosmos. We now know Earth is one planet among eight circling our sun; our sun is part of a swirling galaxy of over one hundred billion other suns; and our galaxy is one of untold billions in the universe. While we do not yet know how many, if any, other biospheres exist on the countless worlds orbiting countless other suns, we stand at the precipice of a new era of discovery, enabled by powerful new facilities able to peer across the light years into the atmospheres of planets similar to our own. This article is an adaptation of a science case document (SCDD) developed for the NASA Astrophysics Flagship mission the Habitable Worlds Observatory (HWO) Science, Technology, and Architecture Review Team (START) Living Worlds Community Working Group.
Metrology of Complexity and Implications for the Study of the Emergence of Life
arXiv (Cornell University) · 2026-02-20
articleOpen access1st authorCorrespondingOne of the longest standing open problems in science is how life arises from non-living matter. If it is possible to measure this transition in the lab, then it might be possible to understand the physical mechanisms by which the emergence of life occurs, which so far have evaded scientific understanding. A significant hurdle is the lack of standards or a framework for cross comparison across different experimental contexts and planetary environments. In this essay, I review current challenges in experimental approaches to origin of life chemistry, focusing on those associated with quantifying experimental selectivity versus de novo generation of molecular complexity, and I highlight new methods using molecular assembly theory to measure molecular complexity. This metrology-centered approach can enable rigorous testing of hypotheses about the cascade of major transitions in molecular order marking the emergence of life, while potentially bridging traditional divides between metabolism-first and genetics-first scenarios. Grounding the study of life's origins in measurable complexity has significant implications for the search for life beyond Earth, suggesting paths toward theory-driven detection of biological complexity in diverse planetary contexts. As the field moves forward, standardized measurements of molecular complexity may help unify currently disparate approaches to understanding how matter transforms to life. Much remains to be done in this exciting frontier.
ArXiv.org · 2026-01-14
articleOpen accessThe discovery of a biosphere on another planet would transform how we view ourselves, and our planet Earth, in relation to the rest of the cosmos. We now know Earth is one planet among eight circling our sun; our sun is part of a swirling galaxy of over one hundred billion other suns; and our galaxy is one of untold billions in the universe. While we do not yet know how many, if any, other biospheres exist on the countless worlds orbiting countless other suns, we stand at the precipice of a new era of discovery, enabled by powerful new facilities able to peer across the light years into the atmospheres of planets similar to our own. This article is an adaptation of a science case document (SCDD) developed for the NASA Astrophysics Flagship mission the Habitable Worlds Observatory (HWO) Science, Technology, and Architecture Review Team (START) Living Worlds Community Working Group.
CBRdb: A Cheminformatic Database for Biochemical Reaction Analysis
ChemRxiv · 2026-04-02
articleSenior authorWe present CBR-db, a database with detailed chemical properties data for biochemical compounds and reactions. We provide the first chemically consistent analyses and detailed chemical properties data for a biologically relevant set of 148,673 reactions and 18,716 small molecules derived from the Kyoto Encyclopedia of Genes and Genomes (KEGG) and the ATLAS of Biochemistry. CBR-db provides detailed atom tracking, reaction similarity classification, compound properties, chiral centers, molecular assembly indices, and thermodynamic properties. CBR-db is designed to be continuously updated, open source, and reproducible. This report highlights the cheminformatic data, explains the curation and dataset, and highlights the data’s utility for researchers working at the intersection of chemical properties and biology. We anticipate a broad range of potential applications for these data, given their position at the intersection of cheminformatics and bioinformatics, including for researchers interested in molecular properties and reaction mechanisms found in metabolism, the chemical underpinnings of synthetic biochemical design and engineering, and how the origins and evolution of biochemistry have selected among properties of molecules and reactions within chemical space.
ArXiv.org · 2026-01-02
articleOpen accessSenior authorAssembly theory (AT) introduces causation as a material property and establishes a metrology for objects produced by evolution and selection. The physical scale of causation is quantified by the assembly index, defined as the minimum number of recursive steps necessary to make an object. Observing countable copies of high assembly index objects indicates a mechanism producing them is persistent, such that the object's environment constructs a memory that traps causation within a contingent chain. Copy number and assembly index together underlie a standardized metrology for detecting causation (assembly index) and contingency (copy number). These allow a precise definition of an assembly threshold that demarcates life (and its derivative agential, intelligent, and technological forms and artifacts) as structures with persistent copies in regimes of deep causal possibility. In introducing a fundamental concept of material causation to quantify and measure life, AT represents a departure from prior theories of causation, such as interventional ones, which have so far proven incompatible with fundamental physics. We discuss how AT's concept of causation provides the foundation for a theory of physics that allows precise and testable concept of "life", and in which novelty, contingency and the potential for open-endedness are fundamental, and determinism is emergent from selection along assembled lineages.
Recent grants
Frequent coauthors
- 69 shared
Edward W. Schwieterman
- 34 shared
Paul Davies
Arizona State University
- 31 shared
Shawn Domagal-Goldman
- 31 shared
Nancy Y. Kiang
- 31 shared
Harrison B. Smith
Blue Marble Space
- 26 shared
Marcelo Gleiser
- 24 shared
Hyunju Kim
Kyungpook National University
- 24 shared
Cole Mathis
Arizona State University
Labs
Education
- 2010
Ph.D., Physics and Astronomy
Dartmouth College
- 2005
B.S., Physics
Florida Institute of Technology
- 2003
Other, Math/Science/Pre-Engineering
Cape Cod Community College
Awards & honors
- Stanley Miller Early Career Award by the International Socie…
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