The recent finding of abundant nickel in a previously waterlogged area of Mars provides further evidence that the red planet might have once supported conditions favorable for life.
In Neretva Vallis, an ancient water channel leading to the Jezero Crater delta, researchers have discovered nickel in concentrations higher than previously recorded in Martian bedrock. This discovery, set within the broader geological context, offers insights into the region’s chemical history and adds another element to understanding Mars’ past habitability.
“While nickel has been identified on Mars before, this detection is the most substantial outside of iron-nickel meteorites found on the planet’s surface,” planetary scientist Henry Manelski from Purdue University shared with ScienceAlert.
“Typically, nickel is a trace element on Earth and Mars’ surfaces, as most of it moves into the planets’ cores during their formation. The significant amount we’ve found on the surface imposes unique constraints on the formation and alteration of these rocks.”
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Nickel is not particularly rare on Mars, but it is usually encountered in meteorite fragments dispersed across the surface.
In 2024, NASA’s Perseverance rover traversed the dry Neretva Vallis and encountered unusual rocks, including a notably pale section of exposed bedrock dubbed Bright Angel by scientists.
Bright Angel was found to exhibit intriguing features often linked to microbial activity on Earth, such as iron-sulfide minerals akin to pyrite—a mineral commonly found in microbe-rich environments—and organic compounds.
During its operations, Perseverance gathered compositional data on numerous rocks throughout Neretva Vallis. Manelski and his team examined this data to understand rock formation processes, leading to the discovery of an unusually strong nickel signal.
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Out of 126 sedimentary rocks and eight rock surfaces examined by Perseverance, researchers identified 32 with nickel concentrations reaching up to 1.1 percent by weight. However, it is the additional contents of these rocks that begin to complete the narrative.
“On Earth, nickel-rich iron-sulfide is found in ancient sedimentary rocks. Iron sulfide deteriorates easily in oxygen-rich environments, so its presence in ancient terrestrial rocks serves as evidence that Earth’s early atmosphere was significantly low in oxygen,” Manelski explained.
“This contrasts sharply with another terrestrial environment where nickel is frequently found: laterites, which are highly weathered ancient soils. The presence of nickel in iron-sulfide suggests these rocks likely formed in an oxygen-poor (reducing) environment.”
These minerals also suggest a dynamic, water-rich environment. The rocks of Neretva Vallis seem to have been shaped by water flows moving through sediments, instigating chemical reactions over time.
Researchers propose that nickel might have been introduced via a meteorite and subsequently dissolved and redistributed by water. Interestingly, on Earth, nickel is vital for many organisms, including microbes.
The nickel concentrations observed suggest it could have been available for use by living organisms, although no claims are made regarding the existence of life forms to utilize it.
The rocks analyzed by Perseverance also contained organic compounds, molecules composed of carbon, the fundamental element for all life on Earth. Carbon can originate through various non-biological processes, yet it is essential for life as we know it, similar to water.
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“In our quest to find evidence of life on ancient Mars, drawing parallels to ancient Earth is beneficial. Life 3.5 to 4 billion years ago—the estimated age of Jezero Crater—was dominated by anaerobic microbes,” Manelski stated.
“Our discovery of high nickel concentrations adjacent to our initial finding of organic carbon and macroscopic zones of reduced sulfur implies nickel was bioavailable. This supports the notion that life-sustaining ingredients existed on ancient Mars.”
The findings also spark questions about the timing of these conditions. The rocks of Neretva Vallis might be younger than other areas of Jezero Crater, indicating that habitable environments on Mars were not confined to its earliest epoch.
“Our discovery of a potentially habitable environment for ancient microbial life suggests that searching for biosignatures in older rocks may not always be the right approach,” Manelski noted. “We should remain receptive to intriguing discoveries wherever our rovers venture.”
The research has been published in Nature Communications.
