A Unique Martian Mineral Offers Fresh Clues About Planet’s Past

New analysis revealed in Nature Communications identifies an iron sulfate on Mars that will symbolize a brand-new mineral.

Sulfur is frequent on Mars and combines with different components to kind minerals, particularly sulfates. While most sulfates are extremely soluble and readily dissolve on Earth throughout rainfall, on the dry floor of Mars these minerals can survive for billions of years and protect vital clues on the planet’s early historical past. Each mineral has a novel crystal construction and properties, together with the frequent minerals gypsum and hematite.

Scientists depend on knowledge collected by Mars orbiters to determine minerals on the floor and procure details about former martian environments that will have enabled the formation of those minerals. For practically 20 years, researchers have been puzzled by uncommon, layered iron sulfates with a novel spectral signature.

Now, a research led by Dr. Janice Bishop, senior analysis scientist on the SETI Institute and NASA’s Ames Research Center in California’s Silicon Valley, has recognized and characterised an unusual ferric hydroxysulfate section by combining laboratory experiments with Mars orbital observations. The discovery provides new perception into how warmth, water, and chemical reactions form the martian floor.

“We investigated two sulfate-bearing sites near the vast Valles Marineris canyon system that included mysterious spectral bands seen from orbital data, as well as layered sulfates and intriguing geology,” mentioned Bishop.

The research included a area known as Aram Chaos, positioned northeast of Valles Marineris the place historic water drained away towards decrease areas within the north, and in addition the plateau above Juventae Chasma, a 5-km-deep canyon positioned simply north of Valles Marineris (Figure 1).

Figure 1. Mars Orbiter Laser Altimeter (MOLA) map of Valles Marineris area with greater elevations in crimson and decrease elevations in yellow, inexperienced after which blue tones. — SETI Institute

Juventae Plateau (above Juventae Chasma): Near the cliffs of Valles Marineris, this space holds clues to Mars’s wetter previous. There are indicators of historic water channels throughout the panorama, however scientists discovered sulfates in only one small, low-lying spot, probably left behind when swimming pools of sulfate-rich water slowly dried up, forming hydrated ferrous sulfates. These minerals, together with ferric hydroxysulfate, seem as skinny meter-thick layers occurring each above and beneath basaltic supplies (Figure 2), suggesting they have been heated from lava or ash after formation.

Figure 2. A view of the plateau above Juventae Chasma with compositional models from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument displaying a decrease basalt unit in cyan (basalt-1), polyhydrated sulfates in blue, the ferric hydroxysulfate section in crimson, and a special basalt unit on prime (basalt-2) in medium inexperienced over a High Resolution Imaging Science Experiment (HiRISE) DTM (5x vertical exaggeration). — SETI Institute

“Investigation of the morphologies and stratigraphies of these four compositional units allowed us to determine the age and formation relationships among the different units,” mentioned Dr. Catherine Weitz, a co-author on the research and Senior Scientist on the Planetary Science Institute.

Aram Chaos:

Researchers have noticed sulfate minerals all through the Valles Marineris area, together with within the rugged landscapes often known as chaotic terrains—areas they consider have been carved and formed by highly effective floods up to now. As water regularly dried up, it left behind layered deposits of iron and magnesium sulfates, refined however highly effective clues that Mars was as soon as a lot wetter. In one chaos terrain that shaped inside a former impression crater, the higher layers comprise polyhydrated sulfates, whereas monohydrated and ferric hydroxysulfate layers lie beneath (Figure 3).

Each of those three sulfates has distinct spectral signatures that may be recognized from orbit utilizing the CRISM instrument (Figure 4). While the stratigraphy of those three sulfates was initially puzzling, lab assessments confirmed that heating polyhydrated sulfates to 50°C produces monohydrated varieties, and heating above 100°C produces ferric hydroxysulfate, supporting the concept geothermal warmth brought about the minerals to remodel. Monohydrated and polyhydrated sulfates happen throughout broad areas (inexperienced and blue in Figure 4, respectively), whereas ferric hydroxysulfate is proscribed to just a few small areas (crimson in Figure 4). The warmest geothermal sources probably sat beneath the websites the place ferric hydroxysulfate seems at the moment, though extra could lie buried beneath monohydrated sulfates.

Figure 3. Views of Aram Chaos area. a) Mars Express High Resolution Stereo Camera (HRSC) picture with compositional models from CRISM marking polyhydrated sulfates (PHS) in blue, monohydrated sulfates (MHS) in inexperienced, and ferric hydroxysulfate in crimson (N is in the direction of the correct). b) HiRISE view of area in yellow field the place all three sulfate varieties are in shut proximity (north is up). — SETI Institute

Figure 4. Spectra of the polyhydrated sulfates (blue squares), monohydrated sulfates (inexperienced circles), and ferric hydroxysulfate (crimson diamonds) measured by the CRISM instrument at Aram Chaos and in comparison with laboratory spectra (darkish strains). Note the sharp slender band at 2.236 µm within the ferric hydroxysulfate spectrum. — SETI Institute

Researchers on the SETI Institute and NASA Ames performed lab experiments to find out how these sulfates remodeled—from rozenite (Fe²⁺SO₄·4H₂O) with 4 water molecules per unit cell, to szomolnokite (Fe²⁺SO₄·H₂O) with one, and eventually to ferric hydroxysulfate, which comprises OH as a substitute of H₂O in its construction.

“Our experiments suggest that this ferric hydroxysulfate only forms when hydrated ferrous sulfates are heated in the presence of oxygen,” mentioned postdoctoral researcher Dr. Johannes Meusburger at NASA Ames. “While the changes in the atomic structure are very small, this reaction drastically alters the way these minerals absorb infrared light, which allowed identification of this new mineral on Mars using CRISM (Figure 4).”

The response requires oxygen fuel and produces water (Equation 1). Today, Mars has a skinny ambiance principally consisting of CO2, however nonetheless has sufficient oxygen for this response to proceed and for oxidation of different types of iron as properly.

Equation 1: 4 Fe2+SO4·H2O + O2  4 Fe3+SO4OH + 2H2O

“The material formed in these lab experiments is likely a new mineral due to its unique crystal structure and thermal stability,” mentioned Bishop. “However, scientists must also find it on Earth to officially recognize it as a new mineral.”

Interestingly, this new ferric hydroxysulfate seems structurally much like szomolnokite, a monohydrated ferrous sulfate mineral, however ferric hydroxysulfate varieties extra simply from rozenite, a tetrahydrated mineral.

This transformation from hydrated ferrous sulfates to ferric hydroxysulfate solely occurs at temperatures above 100°C, a lot hotter than what Mars often experiences on the floor. The sulfates at Aram Chaos and Juventae, together with the ferric hydroxysulfate, probably shaped extra lately than the terrain through which they happen, probably through the Amazonian interval (<3 billion years in the past).

This research reveals that warmth from each volcanic exercise on the Juventae Plateau and geothermal vitality under Aram Chaos can rework frequent hydrated sulfates into ferric hydroxysulfate. The findings recommend components of Mars have been chemically and thermally energetic extra lately than scientists as soon as believed—providing new perception into the planet’s dynamic floor and its potential to have supported life.

The paper, Characterization of Ferric Hydroxysulfate on Mars and Implications of the Geochemical Environment Supporting its Formation, is revealed in Nature Communications.

About the SETI Institute

Founded in 1984, the SETI Institute is a non-profit, multi-disciplinary analysis and training group whose mission is to steer humanity’s quest to grasp the origins and prevalence of life and intelligence within the universe and share that data with the world. Our analysis encompasses the bodily and organic sciences and leverages knowledge analytics, machine studying, and superior sign detection applied sciences. The SETI Institute is a distinguished analysis companion for business, academia, and authorities businesses, together with NASA and the National Science Foundation.

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