Cosmic Rays Could Fuel Hidden Life Deep Below Planets
New research suggests extraterrestrial microbes might thrive on radiation-induced energy
Life’s energy sources may extend far beyond the reach of stars. Groundbreaking research indicates that deep within planets and moons, cosmic rays could provide the vital spark for microbial existence, independent of sunlight.
Subsurface Energy Revolution
Scientists at New York University Abu Dhabi (NYUAD) have demonstrated how high-speed cosmic rays, when interacting with subterranean water, can split molecules and release electrons. These fleeting energy packets could sustain hardy microorganisms in environments previously considered uninhabitable. Physicist Dimitra Atri led the study, which explores a new category of potentially life-supporting environments powered by these energetic particles.
Radiolytic Habitable Zones
Cosmic rays, composed of atomic nuclei and electrons traveling at near light speed, create a secondary particle shower upon impact with celestial bodies. This shower penetrates yards beneath the surface, initiating a process called radiolysis. Radiolysis breaks apart water molecules into reactive fragments, including solvated electrons that carry usable energy for cellular processes. On Earth, this phenomenon in deep basalt aquifers generates hydrogen that supports entire microbial communities miles underground, proving that chemistry can replace sunlight as an energy source.
The NYUAD models define a “radiolytic habitable zone” as any depth where radiolysis can meet the basic metabolic needs of life. Unlike the “Goldilocks zone,” which relies on stellar distance for liquid water, this new zone’s parameters are determined by particle energy and local ice thickness.
Icy Worlds Show Promise
Simulations conducted by the NYUAD team for Mars, Europa, and Enceladus, factoring in cosmic ray spectra and crust densities, highlighted Enceladus as a prime candidate. The energy budgets calculated for Enceladus suggest it could potentially support millions of ATP molecules per gram per second in ice just a few feet deep. Mars ranked second due to its thin atmosphere allowing many particles but a crust that rapidly absorbs them. Europa’s thick ice layer distributes energy deeply but also dilutes it significantly.
“This discovery changes the way we think about where life might exist,”
—Dimitra Atri, Principal Investigator at NYUAD CASS
Earth’s Microbes Pave the Way
The existence of life deep within Earth provides a crucial proof of concept. The bacterium Desulforudis audaxviator, found 1.7 miles underground in a South African gold mine, thrives solely on radiolytic hydrogen and sulfate. Genomic studies confirm its ability to independently fix carbon, nitrogen, and sulfur. Similar radiation-driven hydrogen production sustains microbial ecosystems near underwater hydrothermal vents, reinforcing the idea that radiation-released electrons can power life.
Radiation’s Role in Early Life
Beyond sustaining current life, radiation may have been instrumental in life’s very origins. High-energy particles interacting with water and minerals on early Earth could have facilitated the formation of essential biological building blocks like amino acids and sugars. Scientists hypothesize that similar chemical processes might be occurring beneath the surfaces of Mars, Europa, and Enceladus today.
Rethinking Habitable Zones
The concept of the radiolytic habitable zone fundamentally shifts astrobiological exploration away from solely surface conditions. Traditionally, the “Goldilocks zone” focused on orbital regions where liquid surface water can exist. The radiolytic zone, however, broadens the search to underground environments, considering how deeply cosmic rays can deposit energy. Early theoretical work suggested that even thin atmospheres permit cosmic rays to penetrate tens of yards, potentially transforming seemingly barren frozen deserts into energy-rich chemical oases.
This recalibration impacts planetary protection protocols, mission designs, and the search for biosignatures, suggesting vast new areas to investigate for extraterrestrial life. For instance, the European Space Agency’s Rosalind Franklin rover, slated for a 2028 launch, is equipped with a drill capable of reaching 6.6 feet beneath the Martian surface, a depth chosen to avoid surface radiation but now potentially within a radiolytic habitable zone. NASA’s Europa Clipper mission will use radar to map subsurface water pockets, informing future lander designs aimed at these depths.
Upcoming missions, such as a flagship Orbilander mission to Enceladus, are designed to analyze plume particles and conduct surface operations near active fissures, testing for biosignatures. These endeavors increasingly view radiation not merely as a hazard but as a critical indicator of potential energy sources, chemistry, and life hidden beneath planetary surfaces.
