Phosphorus stands as a fundamental constituent essential for all biological processes, integral to biomolecules such as nucleic acids (DNA and RNA), phospholipids, and the energy currency of cells, adenosine triphosphate. It has been posited that phosphide minerals, exemplified by schreibersite, delivered to primordial Earth via meteoritic impacts served as a primary reservoir for prebiotic phosphorus. Planetary scientists traditionally theorized that minuscule quantities of these minerals also arrived on our planet through countless lightning discharges. However, a collaborative endeavor by researchers from the University of Leeds and Yale University has now conclusively demonstrated that lightning strikes played an equally pivotal role in fulfilling this indispensable function.
An illustration of early Earth, as it would have looked around 4 billion years ago. Image credit: Lucy Entwisle.
In the course of their investigation, Benjamin Hess, a Ph.D. candidate at Yale University, and his associates meticulously analyzed an exceptionally substantial and remarkably preserved specimen of fulgurite.
This particular fulgurite was the direct outcome of a lightning strike that occurred at a site in Glen Ellyn, Illinois, in the United States, during the year 2016.
While the team’s initial focus was on unraveling the geological processes underlying fulgurite formation, they experienced a profound fascination upon discovering a significant concentration of schreibersite within their sample.
The phosphorus present on the surface of early Earth was predominantly sequestered within mineral forms that exhibited insolubility in aqueous environments, a characteristic not shared by schreibersite.
“A prevailing hypothesis suggests that the genesis of life on Earth transpired within shallow surface aquatic environments, aligning with Darwin’s renowned concept of the ‘warm little pond’,” stated Hess.
“The majority of theoretical frameworks concerning the abiotic origin of life on Earth’s surface incorporate meteorites as a delivery mechanism for modest quantities of schreibersite.”
“Our research has revealed a comparatively abundant presence of schreibersite within the fulgurite sample under examination.”
“Given the high frequency of lightning strikes on Earth, this implies that the phosphorus requisite for life’s inception on our planet’s surface is not exclusively contingent upon extraterrestrial impacts.”
“Perhaps more significantly, this finding also suggests that the development of life on exoplanets analogous to Earth remains a plausible scenario long after the era of frequent meteoric bombardment has waned.”
The researchers’ estimations indicate that phosphorus minerals generated by terrestrial lightning events surpassed those delivered by meteorites approximately 3.5 billion years ago, a period coinciding with the age of the earliest recognized microfossil evidence. This temporal alignment underscores the critical role of lightning strikes in the evolutionary trajectory that led to the emergence of life on our planet.
Moreover, the less destructive nature of lightning strikes compared to the cataclysmic force of meteor impacts suggests they were considerably less likely to disrupt the delicate evolutionary pathways conducive to the development and diversification of life.
“The intense bombardment phase of the early solar system represents a singular epoch,” remarked Dr. Jason Harvey, a researcher affiliated with the School of Earth and Environment at the University of Leeds.
“As celestial bodies attain their full mass, the influx of additional phosphorus from meteoritic sources dwindles to insignificance.”
“In contrast, lightning is a recurrent phenomenon. Provided that atmospheric conditions are conducive to electrical discharges, elements vital for abiogenesis can be effectively transported to a planet’s surface.”
“This suggests that the emergence of life on terrestrial planets could potentially occur at any point in their geological history.”
“Our groundbreaking research opens avenues for several future research endeavors. These include the identification and comprehensive characterization of freshly formed fulgurites in environments resembling early Earth; in-depth investigations into the effects of rapid thermal heating on other mineral types to facilitate their recognition in the geological record; and further detailed analysis of this exceptionally well-preserved fulgurite to delineate the spectrum of physicochemical processes it encapsulates,” explained Professor Sandra Piazolo, also a researcher at the School of Earth and Environment at the University of Leeds.
“All such studies are instrumental in advancing our comprehension of the profound impact fulgurite has had in dynamically altering Earth’s chemical milieu throughout geological time.”
This seminal research is comprehensively detailed in a publication featured in the esteemed journal Nature Communications.
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B.L. Hess et al. 2021. Lightning strikes as a major facilitator of prebiotic phosphorus reduction on early Earth. Nat Commun 12, 1535; doi: 10.1038/s41467-021-21849-2
