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Phosphates on Mars and Other Planetary Bodies: Their Spectral Properties and Importance

Session: Advancing Mineralogy and Spectroscopy Across the Solar System in Honor of MSA Roebling Medalist M. Darby Dyar

Presenting Author:

Dr. Janice L. Bishop

Authors:

Bishop, Janice L¹, Lane, Melissa D², Dyar, M Darby³

(1) SETI Institute, Mountain View, CA, USA, (2) Fibernetics, Lititz, PA, USA, (3) Planetary Science Institute, Tucson, AZ, USA,

Abstract:

Darby Dyar’s career spans investigations of most classes of minerals and it has been a joy to work with her on several, including phosphates. Phosphorous has been detected on the surface of Mars by several rover missions and phosphate minerals are present in multiple martian meteorites [1], as well as carbonaceous chondrites [2], and returned samples from asteroid Bennu [3]. Characterizing these phosphates on Mars and other planetary bodies provides important implications for geochemistry and astrobiology.

Two decades ago we initiated a study of the spectral properties of phosphate minerals to investigate their presence at Gusev crater [4]. Measuring samples using Mössbauer [5], Thermal-IR (TIR) [6], and Visible/Near-Infrared (VNIR) [7] spectroscopies are enabling detection of these minerals on Mars and other bodies. Phosphate minerals take on many structures built around PO4 tetrahedra, similar to the mineral structures containing SiO4 and SO4 tetrahedra and many of these could be present on Mars. Fe-bearing phosphates have been observed at Jezero crater [8, 9] and nanophase materials at Gale crater may also contain phosphates [10]. Primary phosphates that crystallize from a fluid include apatite (Ca₅(PO₄)₃OH) and triphylite (LiFe²⁺PO₄), while strengite (FePO₄•2H₂O) and vivianite (Fe²⁺Fe²⁺₂(PO₄)₂•8H₂O) are secondary phosphates that form in low temperatures aqueous environments. Whitlockite (Ca₉(MgFe)(PO₄)₆PO₃OH) and apatite are observed in carbonaceous chondrites [2] and Na-rich phosphates are present in the Bennu samples [3].

The Mössbauer parameters, TIR spectra, and extended visible region spectra collected by the Mars Exploration Rovers were used to constrain potential ferric phosphate minerals present along with sulfates at Paso Robles in Gusev Crater [4]. VNIR spectra of Fe-phosphates may also help constrain the types of phosphates present at Jezero crater.

References: [1] Hausrath et al. (2024) Minerals, 14, 591. [2] Martínez M., A. J. Brearley (2025) GCA, 391, 127-143. [3] McCoy T. J. et al. (2025) Nature, 637, 1072-1077. [4] Lane et al. (2008) American Miner., 93, 728-739. [5] Dyar et al. (2014) American Miner., 99, 914–942. [6] Lane & Bishop (2019) Chapter 3, in Remote Compositional Analysis (Cambridge) 42-67. [7] Bishop (2019) Chapter 4, in Remote Compositional Analysis (Cambridge) 68-101. [8] Kizovski T. V. et al. (2025) Nature Communications, 16, 6470. [9] Hurowitz J. A. et al. (2025) LPSC, LVI, #2581. [10] Rampe et al. (2016) American Miner., 101, 678-689.