[PLS] Chris Carr (Georgia Tech)

“Distinguishing life from non-life via molecular frontier orbital energy gaps”

In the 1960s, Fukui and Hoffmann first demonstrated how frontier orbitals, associated with the most loosely bound electrons and their associated unoccupied orbits (e.g., HOMO, LUMO), could be used to predict the course of chemical reactions. Building on this, we propose frontier orbital-derived biosignatures (FOBs) and apply them to amino acids (AAs), key targets in life detection yet common in abiotic contexts. We introduce LUMOS (Life Unveiled via Molecular Orbital Signatures), a statistical framework using the distribution of abundance-weighted HOMO-LUMO gaps (HLGs) in AAs. Abiotic samples exhibit near-uniform HLG distributions, while biotic samples show greater variance and trend towards lower HLGs, reflecting life’s need to regulate reactivity. Across diverse environments, LUMOS distinguishes biotic from abiotic origins with >95% accuracy, suggesting molecular reactivity variation as a universal biosignature. Compatible with existing instruments, LUMOS supports in situ and sample-return analyses. FOBs address the chemical system aspect of NASA’s life definition, offering a necessary but not sufficient criterion for life and guiding complementary measurements for detecting life beyond Earth.

About our speaker: Christopher E. Carr is an Assistant Professor at Georgia Tech in the Daniel Guggenheim School of Aerospace Engineering with a secondary appointment in the School of Earth and Atmospheric Sciences. His research focuses on developing space instrumentation for life detection, particularly using single molecule technologies, and applying this to understanding the origin and limits of life and supporting a sustainable human future on and off Earth. Carr holds degrees in aeronautics/astronautics (SB 1999, SM 2001, MIT), electrical engineering (SB 1999, MIT), and medical physics (ScD 2005, MIT/Harvard), with postdoctoral training in planetary science and molecular biology. He leads the Planetary eXploration Lab (PXL) and co-directs Georgia Tech’s Center for Astrobiology. Dr. Carr also serves as a Scott M. Johnson Fellow in the U.S. Japan Leadership Program; his prior work includes significant contributions in metabolism, aging, and bioastronautics. Recent service work includes advising NASA on space biology and astrobiology, and the National Academies on human Mars exploration.

Planetary Lunch Seminar —

Colloquia topics span the range of research interests of the department’s planetary sciences research program, and the talks are intended to appeal to any graduate students, postdocs, research scientists, and faculty with a background in planetary science. Speakers include members of the MIT community and visitors.

Contact: planetary-org@mit.edu