The elemental constituents of rocks, namely minerals, and their precise chemical makeup offer profound insights into the genesis and evolutionary path of geological formations. On the Martian surface, NASA’s Perseverance rover, augmented with the Planetary Instrument for X-ray Lithochemistry (PIXL), meticulously generates geochemical cartographies of rock exteriors. In a recent scientific investigation, researchers meticulously examined the outcomes derived from over 90,000 chemical analyses conducted by PIXL during its initial 1,100 Martian days. Their findings indicate that the mineralogy within Jezero Crater has undergone extensive interaction with a succession of distinct fluid types across geological epochs. The results have been published in the Journal of Geophysical Research: Planets.
This image from NASA’s Mars Reconnaissance Orbiter shows Jezero Crater on Mars. Image credit: NASA / JPL-Caltech / MSSS / JHU-APL.
Within the scope of this inquiry, Eleanor Moreland, a graduate student at Rice University, alongside her esteemed colleagues, deployed the Mineral Identification by Stoichiometry (MIST) algorithm to interpret the comprehensive PIXL datasets.
PIXL operates by subjecting Martian geological samples to X-ray bombardment, thereby elucidating their elemental composition. This process yields geochemical measurements of unparalleled granularity ever procured beyond Earth’s confines, as detailed in the research paper.
“The mineral assemblages we are identifying within Jezero Crater, facilitated by the MIST algorithm, provide compelling evidence for multiple, temporally separated episodes of fluid-induced alteration. This suggests that at various junctures in Mars’ history, these specific volcanic rocks engaged with liquid water, thereby creating conditions potentially conducive to life on more than one occasion,” Moreland stated.
Minerals are precipitated under stringent environmental parameters encompassing temperature, pH, and the chemical milieu of surrounding fluids, rendering them reliable indicators of a planet’s historical trajectory.
In the confines of Jezero Crater, the analysis of 24 distinct mineral species illuminates the volcanic origin of the Martian landscape and its protracted interactions with aqueous environments.
The presence of water leads to the chemical weathering of rocks, subsequently forming salt deposits or clay minerals. The specific mineral species that materialize are contingent upon the prevailing environmental conditions.
The spectrum of minerals identified within the crater bears witness to three distinct categories of fluid-rock interactions, each carrying disparate implications for the potential habitability of the environment.
The inaugural mineralogical assemblage, encompassing compounds such as greenalite, hisingerite, and ferroaluminoceladonite, signifies the influence of localized, high-temperature, acidic fluids. These conditions appear to have been confined to the bedrock situated on the crater floor, which is posited to represent some of the most ancient rock formations investigated in this study.
The aqueous phase involved in this particular episode is considered the least hospitable to nascent life. This is predicated on extensive terrestrial research demonstrating that elevated temperatures and low pH levels can deleteriously affect biological structures.
“These high-temperature, acidic conditions would present the most formidable challenges for life,” commented Rice University researcher Kirsten Siebach.
“However, it is important to note that on Earth, organisms have been observed to thrive even in extreme environments, such as the highly acidic thermal pools found in Yellowstone. Therefore, this finding does not definitively preclude habitability.”
The second group of minerals reflects conditions influenced by moderate, neutral fluids, which are generally considered more amenable to biological existence. These fluids appear to have been prevalent across a broader geographical expanse.
Minerals like minnesotaite and clinoptilolite originated under less extreme thermal regimes and near-neutral pH levels. Minnesotaite was detected in both the crater floor and the upper fan sector, whereas clinoptilolite was exclusively found on the crater floor.
Concluding the classification, the third category is indicative of low-temperature, alkaline fluid interactions, which, from a contemporary Earth-based perspective, are regarded as highly conducive to habitability.
Sepiolite, a mineral commonly observed to form through alteration processes on Earth, developed under moderate temperatures and alkaline conditions. Its presence was documented across all geological units that the rover has surveyed.
The ubiquitous distribution of sepiolite across these varied units underscores a pervasive episode of liquid water activity that fostered habitable conditions within Jezero Crater and contributed to the infilling of sedimentary deposits.
“These mineralogical signatures compellingly suggest that Jezero Crater transitioned from an environment characterized by more aggressive, hot, acidic fluids to one dominated by more neutral and alkaline conditions over time. These are precisely the types of conditions we hypothesize to be increasingly supportive of life,” Moreland elaborated.
Given the inherent limitations in preparing and analyzing Martian samples with the same precision as terrestrial ones, the research team developed an uncertainty propagation model to enhance the robustness of their findings.
Employing a statistical methodology, the MIST algorithm rigorously evaluated mineral identifications by repeatedly factoring in potential sources of error. This iterative process is analogous to how meteorologists generate hurricane track forecasts by running numerous predictive models.
“Our comprehensive error analysis empowers us to assign a quantitative confidence level to each mineral identification,” Moreland explained.
“Not only does MIST contribute valuable intelligence to the Mars 2020 mission’s scientific objectives and decision-making processes, but it is also instrumental in constructing a mineralogical record of Jezero Crater. This archive will undoubtedly prove indispensable should samples eventually be repatriated to Earth.”
The discovered evidence corroborates the hypothesis that Jezero Crater, once the site of an ancient lake, has a complex and dynamic hydrological history.
Each new mineral discovery not only propels scientists closer to resolving the question of whether Mars ever harbored life but also refines Perseverance’s strategic approach to identifying and collecting samples for future return missions.
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Eleanor L. Moreland et al. 2025. Multiple Episodes of Fluid Alteration in Jezero Crater Indicated by MIST Mineral Identifications in PIXL XRF Data From the First 1100 Sols of the Mars 2020 Mission. Journal of Geophysical Research: Planets 130 (9): e2024JE008797; doi: 10.1029/2024JE008797
