Within Jezero crater, NASA’s Perseverance rover has undertaken investigations and collected samples from igneous and sedimentary rock formations. The objective has been to elucidate early Martian geological dynamics, assess its potential for supporting life, and identify any indications of past biological activity. Upon its traversal into Neretva Vallis, situated on the western perimeter of Jezero crater, the rover meticulously examined distinct outcrops of mudstone and conglomerate belonging to the Bright Angel formation. In a newly published scientific paper featured in the journal Nature, researchers present a comprehensive geological, petrographic, and geochemical analysis of these Martian rock specimens.
This artist’s impression showcases Mars as it might have appeared approximately four billion years ago. Credit: M. Kornmesser / ESO.
“The moment the rover entered the Bright Angel region and commenced compositional analyses of the local strata, the research team was immediately struck by the profound divergence from previously observed Martian geology,” stated Dr. Michael Tice, a distinguished geobiologist and astrobiologist affiliated with Texas A&M University.
“These formations exhibited evidence of chemical cycling that is exploitable by organisms on Earth for energy generation.”
“Further, upon intensified scrutiny, we identified phenomena readily explicable by the existence of early Martian life, yet exceedingly challenging to attribute solely to geological processes.”
“Living entities engage in chemical transformations that, given sufficient temporal duration and conducive circumstances, typically occur naturally.”
“Based on our current understanding, the chemistry that shaped these rocks necessitates either elevated temperatures or biological intervention, neither of which is demonstrably present here.”
“Nevertheless, these preliminary findings necessitate rigorous experimentation and, ultimately, ex-situ laboratory examination of the collected samples on Earth to definitively preclude non-biological explanations.”
The Bright Angel formation is characterized by sedimentary rocks that were deposited by aqueous action, encompassing mudstones – which are fine-grained sedimentary rocks composed of silt and clay – and stratified beds that imply a dynamic historical environment marked by fluvial activity and the presence of standing bodies of water.
Leveraging Perseverance’s advanced instrumentation, including the SHERLOC and PIXL spectrometers, the scientific contingent detected organic molecules and intricate mineral assemblages that appear to have originated from redox reactions, a class of chemical processes involving the transfer of electrons. On Earth, such processes are frequently instigated by biological activity.
Among the most compelling observations are microscopic nodules and ‘reaction fronts’ – colloquially termed ‘poppy seeds’ and ‘leopard spots’ by the rover’s operational team – which are notably richer in ferrous iron phosphate (presumed to be vivianite) and iron sulfide (presumed to be greigite).
These specific minerals are typically associated with low-temperature, water-saturated environments and are frequently correlated with microbial metabolic pathways.
“It is not merely the mineralogical composition, but rather their spatial arrangement within these structures that suggests formation through the redox cycling of iron and sulfur,” elaborated Dr. Tice. “On terrestrial planets, phenomena of this nature sometimes develop within sediments where microorganisms metabolize organic matter while ‘respiring’ iron oxides and sulfates.”
“Their existence on Mars naturally prompts inquiry: could analogous processes have transpired on the Red Planet?”
This artistic rendition illustrates NASA’s Perseverance rover positioned on the Martian surface. Image courtesy of NASA / JPL-Caltech.
The SHERLOC instrument identified a Raman spectral signature, specifically the G-band, indicative of organic carbon, within multiple rock samples from the Bright Angel formation. The most pronounced signals emanated from a location designated as Apollo Temple, where both vivianite and greigite were found in their highest concentrations.
“This spatial concurrence of organic compounds and redox-sensitive minerals is exceptionally persuasive,” remarked Dr. Tice. “It suggests that organic molecules might have played a consequential role in driving the chemical reactions responsible for the genesis of these mineral formations.”
“It is imperative to clarify that the term ‘organic’ does not inherently connote biological origin.”
“It simply signifies the presence of a substantial number of carbon-carbon bonds.”
“Alternative, non-biological pathways exist that can generate such bonds. The type of organic material detected here could have arisen from abiotic processes, or it could have been a product of living organisms.”
“If produced by organisms, it would subsequently undergo degradation via chemical reactions, radiation, or thermal exposure to yield the observed G-band signature.”
The research posits two plausible scenarios: one involving abiotic reactions driven by geochemical processes, and another where microbial life may have influenced these reactions, mirroring terrestrial occurrences.
Remarkably, while certain characteristics of the nodules and reaction fronts are potentially attributable to abiotic interactions between organic matter and iron, the known geochemical mechanisms capable of generating the associated sulfur features typically require relatively high temperatures.
“All analytical avenues available to us on the rover indicate that these rocks were never subjected to temperatures high enough to produce the ‘leopard spots’ and ‘poppy seeds’,” stated Dr. Tice. “Consequently, we must seriously entertain the hypothesis that these features were formed by microbial life, akin to bacteria, inhabiting the ancient lakebed sediments of Mars over three billion years ago.”
This depiction outlines Perseverance’s trajectory through Neretva Vallis and provides visual representations of the Bright Angel formation. Image attribution: Hurowitz et al., doi: 10.1038/s41586-025-09413-0.
Although the research team stresses that the current evidence does not constitute definitive proof of past life, the discoveries align with NASA’s established criteria for potential biosignatures – characteristics that necessitate further investigation to ascertain their biological or abiotic origins.
Perseverance successfully procured a core sample from the Bright Angel formation, designated Sapphire Canyon, which has since been hermetically sealed within a tube aboard the rover.
This particular sample is among those designated as high priority for potential retrieval and return to Earth via a future mission.
“Transporting this sample back to Earth would grant us access to analytical instruments possessing significantly greater sensitivity than any currently deployable on Mars,” Dr. Tice explained. “We would be equipped to examine the isotopic composition of the organic matter, analyze the micro-scale mineralogy, and even conduct searches for potential microfossils.”
“Furthermore, we could perform more extensive tests to determine the maximum temperatures these rocks have experienced, thereby conclusively evaluating whether high-temperature geochemical processes remain the most parsimonious explanation for the putative biosignatures.”
“The parallels between extraterrestrial and terrestrial geological processes are striking, albeit with one notable distinction.”
“The fascinating aspect is how life might have utilized comparable chemical pathways on Earth and Mars concurrently. We observe evidence of microorganisms interacting with iron and sulfur via organic matter in a manner analogous to terrestrial rocks of the same age; however, the precise features observed on Mars are not discernible in our planet’s ancient rock strata.”
“Terrestrial geological processes, such as plate tectonics, have elevated the temperatures of our rocks to an extent that precludes their preservation in this specific state. Witnessing such features on another celestial body represents a truly extraordinary and remarkable observational opportunity.”
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J.A. Hurowitz et al. 2025. Redox-driven mineral and organic associations in Jezero Crater, Mars. Nature 645, 332-340; doi: 10.1038/s41586-025-09413-0
This article is based on a press release disseminated by Texas A&M University.
