The discovery of large amounts of nickel in the once water-filled surface of Mars provides further evidence that the red planet may have once provided suitable conditions for life.
In Neretva Vallis, an ancient channel that once carried water to the slopes of Jezero Crater, researchers found more nickel than ever before in a Martian rock. Placed in its broad geological context, the metal provides clues about the chemical history of the region and adds a new dimension to the game of the planet’s past.
“Although nickel has been found on Mars before, this is the strongest detection from outside of an iron-nickel meteorite found on the Martian surface,” planetary scientist Henry Manelski of Purdue University told ScienceAlert.
“In general, nickel is a relatively recent element on Earth and Mars because most of it migrated to parts of the planets during their formation. The large amount we detected in the surface water places unique constraints on how these rocks were formed and later modified.”
Nickel is rarely found on Mars, but is often found in scattered meteorite fragments.
In 2024, when NASA’s Perseverance rover rolled into the long-dry Neretva Vallis, it encountered unusual rocks, including an unusual section of exposed rock that scientists named Bright Angel.
The bright angel was found to contain some curious elements that are often associated with biological activity on Earth, including iron-sulfide minerals similar to pyrite – minerals that are often found in areas with microbes – and organic compounds.
As part of its mission, Perseverance collected structural data on many rocks throughout the Neretva Vallis, which Manelski and his colleagues analyzed for clues about how the rocks formed. It was during this analysis that a strong nickel signal emerged.
frameborder = “0” allow = “accelerometer; autoplay; write to clipboard; encrypted media; gyroscope; picture-in-picture; web ratio” referrerpolicy=”start-hard-when-space” allowfullscreen>Among the 126 sedimentary rocks and eight rocks studied by Perseverance, the researchers found 32 with nickel concentrations up to 1.1 percent by weight. But it’s what was in those rocks that starts to piece the story together.
“Nickel-rich iron-sulfide is observed on Earth in old sedimentary rocks. Iron sulfide weathers easily in areas with a lot of oxygen, so its presence in the old rocks of the world is another evidence used to show that the first atmosphere of the Earth was once very poor,” Manelski explained.
“This is very different from another environment in which nickel is often found on Earth: lateites, which have very dense ancient soils. The observation of nickel in iron-sulfide suggests that these rocks may have formed in a reducing environment (poor in oxygen).
The presence of these minerals also indicates a freshwater environment. The rocks in Neretva Vallis appear to have been formed by the flow of water moving through the sediment, transporting chemicals over time.
The researchers believe that the nickel may have been brought as part of a meteorite, then dissolved and redistributed in water. But here’s where it gets interesting: On Earth, nickel is essential for many organisms, including microbes.
The levels of nickel the researchers found suggest that it may have been available for use by living things (although they don’t make claims that any life was around).
The rocks analyzed by Perseverance also show the presence of organic compounds, molecules that contain carbon, the substance on which all life on Earth is based. Carbon can form in many unnatural ways, but, like water, it is something that life as we know it cannot do without.
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“While we are looking for evidence of life on ancient Mars, it is better to get closer to life on the ancient Earth. Life around 3.5 to 4 billion years ago – about the age of Jezero Crater – was dominated by anaerobic organisms,” said Manelski.
“Our detection of abundant nickel deposits directly adjacent to our first detection of carbon and large areas of reduced sulfur suggests that nickel was present in organic matter. This further supports the hypothesis that life forms were present on ancient Mars.”
The findings also raise questions about when these conditions occurred. The rocks in Neretva Vallis may be smaller than other parts of Jezero Crater, suggesting that habitable areas on Mars were not limited to its early history.
“What we found about the apparently habitable environment for ancient microbial life suggests that our search for biosignatures in ancient rocks may be wrong,” said Manelski, “and we should always be mindful of exciting discoveries wherever our explorers explore.”
The findings were published in Nature Communication.
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