The recent discovery of a key mineral has reshaped our scientific understanding of what Mars looked like in the past. Researchers at UTSA are exploring whether Mars could have once been habitable by investigating new mineral evidence that suggests the red planet may have sequestered large amounts of CO2 and the relationship of carbon cycle on Mars with iron, chlorine and bromine.
Last April, NASA announced that its Curiosity rover had made a groundbreaking discovery. Drill samples taken from the rover at the Gale crater were analyzed and found to contain high levels of iron carbonate siderite, a mineral composed primarily of iron, carbon and oxygen. This finding is significant because the formation of siderite typically requires a stable, aqueous environment that is rich in ferrous iron and carbon-containing anions, carbonate and bicarbonate.
Kaushik Mitra, an assistant professor in the UTSA Department of Earth and Planetary Sciences, has conducted a laboratory-based experimental study to investigate the formation of ferric iron-bearing minerals that were detected at Gale crater on Mars along with siderite by the Curiosity rover. The team is hoping to uncover the processes that led to the juxtaposition of ferrous and ferric iron-bearing minerals.
“If we want to know if life ever existed there, understanding how these minerals are produced and destroyed is a key piece of the puzzle.”
“This detection of abundant, crystalline, pure ferrous carbonate along with ferric minerals like goethite and akaganeite on Mars is a groundbreaking discovery,” Mitra said. “Our lab group focuses on redox processes in extraterrestrial aqueous systems, and better understanding this discovery became an important and urgent project.”
Mitra’s research is challenging the conventional explanations of strong acids or sunlight for the alteration of siderite to ferric minerals and instead proposes that the mineral was oxidized in by brines containing chlorine and bromine salts. The experiments, conducted in Mitra’s newly formed Laboratory for Experimental & Aqueous Planetology (LEAP) at UTSA, simulate Martian conditions to observe how siderite behaves in various fluid chemistries.
“If we want to know if life ever existed there, understanding how these minerals are produced and destroyed is a key piece of the puzzle,” Mitra added.
The research team’s findings suggest acidic conditions alone cannot explain how the siderite was formed. Instead, Mitra’s team suggests brines may be responsible for forming these iron-rich minerals under Martian conditions.
“This research changes how we think about Mars’ environment,” Mitra said. “Instead of just being acidic and unfriendly, parts of Mars may have had more complex and varied chemistry — possibly with liquid water that wasn’t as straightforward as we thought.”
Mitra is joined by Lauren Malesky, a geosciences graduate student at UTSA, who is assisting Mitra with the experiments and data analysis. Additionally, the team is comprised of Michael T. Thorpe, assistant research scientist at the University of Maryland and NASA Goddard Space Flight Center, and Ana Stevanovic, research core director for the Kleberg Advanced Microscopy Center at UTSA. The project is supported by Mitra’s UTSA Faculty Start-Up Fund grant and includes funding from NASA.
The team’s findings were recently published in the Proceedings of the National Academy of Sciences (PNAS), a leading multidisciplinary journal, in an article entitled, “Siderite and Ferric Oxyhydroxides Imply Interlinked Carbon, Iron, & Halogen Cycles on Mars.”
