The identification of substantial nickel deposits within a region of Mars previously characterized by significant water activity furnishes additional compelling evidence that the red planet might have once possessed an environment conducive to life.
Within Neretva Vallis, an ancient watercourse that once channeled liquid into the Jezero Crater delta, scientists have identified nickel at unprecedented concentrations within Martian bedrock. When viewed within its broader geological framework, this metallic element provides valuable insights into the region’s chemical evolution and contributes a vital element to our understanding of the planet’s past potential for habitability.
“While traces of nickel have been previously observed on Mars, this represents our most definitive detection to date, excluding the iron-nickel meteorites discovered on the Martian surface,” stated planetary scientist Henry Manelski from Purdue University in an interview with ScienceAlert.
“Typically, nickel is considered a trace element on both Earth’s and Mars’ surfaces, primarily because the overwhelming majority of it segregates into the planets’ metallic cores during their formation. The considerable quantity we have detected on the surface imposes significant constraints on the geological processes involved in the genesis and subsequent transformation of these rock formations.”
Nickel is not an exceptionally rare element on Mars; however, it is predominantly encountered in fragments of meteorites disseminated across its expanse.
In the year 2024, while NASA’s Perseverance rover traversed the long-arid Neretva Vallis, it encountered a series of anomalous geological formations, including a noticeably pale stratum of exposed bedrock that researchers subsequently designated as Bright Angel.
The Bright Angel formation exhibits distinctive characteristics frequently indicative of microbial activity on Earth. These include the presence of iron-sulfide minerals akin to pyrite – a mineral commonly found in environments teeming with microbial life – and the detection of organic compounds.
As part of its scientific mission, Perseverance meticulously gathered compositional data from numerous rock samples across Neretva Vallis. Manelski and his research associates undertook a thorough examination of this data, seeking indicators of the rocks’ formation mechanisms. It was during this analytical phase that a remarkably pronounced nickel signature became apparent.
Out of a total of 126 sedimentary rock samples and eight rock surfaces investigated by Perseverance, the research team identified 32 specimens containing nickel concentrations reaching up to 1.1 percent by mass. However, it is the co-occurrence of other elements within these rocks that truly illuminates the narrative.
“Nickel-rich iron-sulfide formations are observed on Earth within ancient sedimentary rock strata. Iron sulfide undergoes rapid weathering in oxygen-rich environments, consequently, its presence in ancient terrestrial rocks serves as a key piece of evidence supporting the hypothesis that Earth’s primordial atmosphere was markedly oxygen-deficient,” Manelski elucidated.
“This presents a profound contrast to another terrestrial environment where nickel is frequently encountered: laterites, which are highly weathered ancient soil profiles. The observation of nickel within iron-sulfide suggests that these rock formations likely originated in a reducing (oxygen-poor) milieu.”
The existence of these mineral deposits also points towards a dynamic aqueous environment. The geological formations of Neretva Vallis appear to have been sculpted by the flow of water through sedimentary layers, facilitating chemical transformations over extended periods.
The researchers posit that nickel may have been introduced via meteorite impact, subsequently becoming dissolved and dispersed by water. However, the implications become more profound: on Earth, nickel is a vital element for a multitude of organisms, including microorganisms.
The nickel concentrations identified by the research team imply that it could have been readily accessible for biological utilization (though no assertions are made regarding the actual presence of life capable of exploiting it).
The rock samples analyzed by Perseverance also revealed the presence of organic compounds – molecular structures containing carbon, the foundational element of all known life on Earth. While carbon can indeed arise from numerous non-biological processes, it is, alongside water, an indispensable constituent for life as we understand it.
“In our ongoing pursuit of evidence for ancient Martian life, it proves beneficial to draw parallels with the conditions of ancient Earth. Life approximately 3.5 to 4 billion years ago – corresponding to the estimated age of the Jezero Crater – was predominantly comprised of anaerobic microorganisms,” Manelski remarked.
“Our detection of elevated nickel abundances in close proximity to our initial discovery of organic carbon and macroscopic zones of reduced sulfur strongly suggests that nickel was biologically available. This finding further bolsters the premise that the essential components for life were present on ancient Mars.”
These discoveries also prompt inquiries into the temporal span during which these conditions persisted. The geological formations within Neretva Vallis may be younger than other sections of the Jezero Crater, implying that potentially habitable environments on Mars were not exclusively confined to its earliest epochs.
“Our identification of an environment seemingly suitable for ancient microbial existence suggests that our search for biosignatures in progressively older rock strata might be somewhat misdirected,” Manelski commented, “and we should maintain an open and receptive attitude towards significant discoveries, irrespective of their location explored by our rovers.”
The research findings have been formally published in Nature Communications.
