How UNLV’s Ranjani Murali hunted for dark oxygen two miles down—and brought some home

How UNLV’s Ranjani Murali hunted for dark oxygen two miles down—and brought some home Las Vegas Weekly Staff Thu, Oct 1, 2026 (2 a.m.) In March of this year, a team of scientists led by Emil Ruff, who holds a Ph.D. in microbial ecology, descended into a 2.2‑mile‑deep mineshaft just outside Johannesburg, South Africa. The NASA‑funded mission aimed to examine a billion‑year‑old brine uncovered after an earthquake fractured a tunnel wall. The brine, which is radioactive, harbors microbes, argon, phosphorus and oxygen. Researchers refer to this subsurface oxygen as “dark oxygen” because it forms without photosynthesis. Ranjani Murali, an adjunct professor of microbial biology and genomics at UNLV, joined the expedition alongside Sujung Lim, a postdoctoral researcher in Murali’s lab. Murali explained—or tried to; I didn’t walk biology—what dark oxygen is, what it might signify, and UNLV’s role in studying it. **Please explain this to me as you would to a middle‑schooler.** I’ll do my best. **What is your field of study?** Environmental microbiology. I investigate how microorganisms adapt to diverse ecosystems, ranging from scalding hot springs to frigid polar settings and the deep ocean. Typically, an adaptation enables them to survive in those conditions, produce energy and grow. I am keen to uncover the mechanisms behind those adaptations. **And how did you end up two miles underground?** This work stems from a collaboration between me and many others, but the principal investigator, Dr. Emil Ruff, and I have partnered for years. We first met at the Microbial Diversity Summer School in Woods Hole, Massachusetts. One area where our interests converged was his observation of oxygen buildup in places where it was not anticipated, while my laboratory specializes in oxygen‑reducing enzymes and aerobic metabolism. **What is happening in the Moab Khotsong mine?** The current research group is examining organisms that use oxygen and reside beneath the surface. In the subsurface, the prevailing view had been that only anaerobic life—organisms intolerant of oxygen—existed, primarily cycling chemical compounds in oxygen‑free settings. Yet our findings, and ongoing work, show that even in the absence of light, oxygen can be generated. Most planetary oxygen originates from plants and microorganisms such as cyanobacteria through photosynthesis, a process that depends on light. Consequently, we did not expect to find oxygen in light‑starved environments like mines or the deep sea. … We hypothesize that microbes chemically break down compounds such as nitric oxide and chlorite, which are present in those settings, to produce oxygen. **Is this dark oxygen sustaining life?** Radiolysis generates energy‑rich particles that can split water in ways not otherwise conceivable. … Radioactive substances are harmful to all of us because they emit those particles, which then dismantle otherwise stable compounds. When those particles encounter water, they can cleave it into oxygen. Because the mine contains radioactive minerals like uranium, it yields