In 2024, NASA’s Perseverance rover found surprising levels of Nickel in the Martian bedrock of an ancient river channel, called Neretva Vallis, which flowed into the Jezero crater. A new study, published in Nature Communications, has taken a closer look at the data collected from the region and researchers are seeing what could be remnants of ancient Martian life.
Nickel as a biosignature
Although nickel is not typically thought of as a major component of human life, it is important in many microbial metabolism functions. For example, nickel is a requirement for the Wood-Ljungdahl (W-L) pathway—an ancient, energy-efficient anaerobic process utilized by bacteria and archaea to fix carbon dioxide. The reverse of this process also requires nickel and has been observed in some species of sulfate-reducing bacteria, for the decomposition of organic matter.
“In particular, Ni is an essential component of enzymes used by methanogenic archaea and many bacterial species. Ni is vital to the metabolism of methanogenic organisms, such that a decrease in the Ni content of Earth’s oceans in the Archean is hypothesized to have caused a collapse in atmospheric methane preceding the Great Oxidation Event,” explain the study authors.
Furthermore, most of a planet’s nickel is expected to be in its core. So, higher concentrations on or near the surface are typically unexpected, unless deposited there through other means. Researchers can use information from surrounding rocks to determine more about the origin, such as whether the nickel likely came from volcanic, meteoritic, or other sources.
Unexpected nickel concentrations in Neretva Vallis
Samples picked up by Perseverance showed nickel concentrations of up to 1.1 wt.% in Neretva Vallis, representing the highest-ever nickel concentrations detected in Martian bedrock. Nickel was detected at 0.12 wt.% or higher in 32 out of the 126 distinct rock targets analyzed by Perseverance’s remote Laser Induced Breakdown Spectroscopy (LIBS) technique. The team notes that many of these samples were near iron-rich rocks, which they say indicates the presence of nickel in an iron-bearing phase. Scans also identified nickel rich regions in veins of magnesium sulfate.
“There are few processes capable of enriching Ni to the extreme levels seen in Neretva Vallis and any such explanation must also be consistent with the bulk geochemistry and geologic context of Neretva Vallis sedimentary rocks. In particular, the observation that Ni is found concentrated in dispersed Fe-sulfides and diagenetic sulfates within Mg poor mudstones must be considered,” the study authors write.
Although the team is still uncertain of the exact origins of these nickel-rich regions, they say that the geochemistry and textures resemble ancient Earth rocks where life first emerged. They say that sedimentary Fe-sulfides on Earth, similar to those found in certain regions of Neretva Vallis, are believed to form by microbial sulfate reduction in the presence of Fe-bearing minerals.
The researchers say that the thermochemical reduction of sulfate at high temperatures is another possible explanation, but there is no evidence for the metamorphism or burial to the depths required for thermochemical sulfate reduction, and that the hydrated sulfate minerals and clays there indicate low-temperature processes. The authors note that previous findings of organic matter and iron-sulfides spurred the designation of a “potential biosignature” for the same reason.
They explain, “The results of our investigation of sedimentary rocks derived from Noachian (~4.1-3.7 Gya) materials in the Jezero watershed invite comparisons with an early Earth environment and a terrestrial biosphere that developed around the same time as these rocks. While the observations presented in this work do not necessarily imply that the distribution of Ni is related to a biological process, the presence of strong enrichments suggests it was bioavailable.
“As an element essential to the earliest known forms of life on Earth, and a particularly scarce trace metal, the elevated concentrations of Ni in the Beaver Falls workspace—co-located with organic matter—offers an intriguing hint of past organic driven redox processes on Mars.”
Non-biological possibilities
The instruments available on Perseverance cannot perform the detailed isotopic or trace metal analyses needed to confirm origins or biological links, so the origins of nickel in Neretva Vallis remain uncertain. However, the study authors do present some non-biological possibilities as well.
The team says that the nickel may have been delivered by a meteorite, then dissolved and redistributed by water flowing through the region at the time. They say another possibility is that nickel accumulated from intense chemical weathering of an ultramafic protolith—a type of igneous or sedimentary rock, primarily composed of iron and magnesium-rich minerals, but also nickel.
The researchers plan on further analysis when the collected rock samples are brought back to Earth. They say this could clarify the source and significance of nickel enrichment, potentially revealing more about Mars’ history and its potential for ancient life. https://phys.org/news/2026-04-high-nickel-martian-bedrock-potential.html
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