Chinese Study Reveals Energy Source for Deep Subsurface Microbes

In a groundbreaking study published in the journal *Science Advances* on July 19, 2025, researchers from the Chinese Academy of Sciences (CAS) have challenged the long-standing belief that all life depends on sunlight. The study, led by Professors He Hongping and Zhu Jianxi from the Guangzhou Institute of Geochemistry, reveals that microbes residing in deep subsurface environments can derive energy from chemical reactions facilitated by crustal faulting, thereby unveiling the complexities of life in extreme conditions.

Historically, deep subsurface regions of the Earth have been considered inhospitable to life due to the lack of sunlight and organic matter. However, recent discoveries have shown that these areas harbor a vibrant biosphere filled with diverse microorganisms. According to the study, these microbes utilize hydrogen (H₂) produced from abiotic redox reactions during water-rock interactions as their primary energy source. Moreover, the research team was able to elucidate the origins of oxidants crucial for microbial metabolism, a topic that had previously remained unclear.

Through experimental simulations of crustal faulting activities, the researchers discovered that the fracturing of rocks produces free radicals that can decompose water, leading to the generation of hydrogen and other oxidants, such as hydrogen peroxide (H₂O₂). This process creates a distinct redox gradient within fracture systems, which can alter the oxidation state of iron (Fe) present in groundwater and rocks, facilitating a cycle that is essential for microbial life.

"In microbe-rich fracture zones, the hydrogen production driven by faulting activities can be up to 100,000 times greater than that from other known sources, such as serpentinization and radiolysis," stated Professor He Hongping. This significant increase in hydrogen production not only highlights the role of crustal faults in sustaining microbial metabolism but also influences the geochemical processes of critical elements, including carbon, nitrogen, and sulfur.

The implications of this research extend beyond Earth. Professors He and Zhu suggest that similar fracture systems on other Earth-like planets could provide habitable conditions for extraterrestrial life, thus opening new avenues for astrobiological research. They emphasize the need for continued exploration of deep subsurface environments to further understand the diversity of life and its energy sources.

The study received funding from the National Science Fund for Distinguished Young Scholars, along with support from the Strategic Priority Research Program of CAS, among other sources. This research represents a significant advancement in our understanding of extremophiles and the energy dynamics of Earth's subsurface biosphere, reinforcing the idea that life can thrive in environments previously thought to be uninhabitable.

As scientists continue to unravel the mysteries of life on Earth and beyond, this study serves as a reminder of the resilience and adaptability of living organisms in even the most challenging environments.