About

John Mustard is a professor in the Department of Earth, Environmental & Planetary Sciences at Brown University. His research focuses on the processes that modify solid surfaces and the spatial and temporal scales that control environmental processes on the Earth. He is involved in studying a range of topics including environmental science, oceans, ice and atmospheres, and planetary geoscience. Professor Mustard has contributed to various high-profile scientific discussions and discoveries, including insights into lunar science from NASA’s Artemis mission, the detection of organic molecules on Mars by the Curiosity rover, and the assessment of water frost on Mars’ volcanoes. His work is recognized for its impact on understanding planetary surfaces and the history of water and habitability in the solar system. He has also been part of teams evaluating NASA’s Mars Sample Return architecture proposals, reflecting his active engagement in planetary exploration and research.

Research topics

• Geology
• Astrobiology
• Geochemistry
• Mineralogy
• Remote sensing

Selected publications

• Preserved altered olivine in the Jezero western rim, Mars

  2026-04-27

  articleOpen access

  Impact craters expose otherwise inaccessible records of subsurface composition and early planetary processes on Mars. Using orbital hyperspectral data, we report partially altered olivine in the Jezero western rim. The rim olivine exhibits strong hydration and Fe/Mg-OH absorptions with negligible carbonate, contrasting with the CO₂-dominated carbonation of the regional olivine and indicating water-dominated alteration favoring phyllosilicate formation. The persistence of primary olivine alongside alteration products suggests water-rock interaction was either temporally limited or confined to specific horizons within the target stratigraphy. iSALE-2D impact simulations demonstrate that outer rim materials originated from shallow depths (<1 km) and experienced minimal shock (<2 GPa, <180°C), well below the stability thresholds of olivine and phyllosilicates. We interpret these assemblages as pre-impact lithologies preserving possible serpentinization in the shallow Noachian crust predating both Jezero crater formation and the regional carbonation regime, potentially recording an early habitable environment sustained by hydrogen production from olivine-water reactions.

  PublisherOA PDFDOI

• Biosignatures in Terrestrial Altered Volcanic Rocks — Focus on Nitrogen as a Key Biogeochemical Tracer

  2026-03-14

  articleOpen access

  Here we synthesize work conducted at Lehigh University and the Pheasant Memorial Laboratory in Misasa, Japan (Institute for Planetary Materials, Okayama University), focusing on nitrogen (N) behavior in altered basaltic glasses and related secondary minerals that serve as terrestrial analogs for Martian surface/subsurface alteration. Initial proof of concept work demonstrated N enrichment in aqueously altered seafloor volcanic glasses with biotic influence suggested by δ15N signatures and microtubular textures (Bebout et al., 2018). Recently, this approach has been applied to study of hyaloclastites from Antarctica and Iceland that serve as better analogs for Martian hydrothermal alteration processes. This pursuit, employing advanced microanalytical and microscopic techniques, has extended knowledge of the modes of incorporation and isotopic signatures of N as a valuable tracer of biogeochemical processes in such materials (Nikitczuk et al., 2022a,b). In new studies, we have investigated Icelandic amygdules in altered basalts that are mineralogical and geochemical analogs for those on the Noachian Mars surface (Ehlmann et al., 2012; Weisenberger and Selbekk, 2009). In addition, we examined erupted basaltic tephra from Surtsey Island, Iceland which, together with the amygdules, provide records of the alteration of very young erupted mafic volcanics (for Surtsey,

  PublisherDOI

• Particle size and albedo effects on emissivity spectra of lunar analog minerals and rocks in the intermediate infrared region

  Icarus · 2025-07-02

  article
  PublisherDOI

• Impact Modeling and Remote Sensing of Jezero Crater Rim: Implications for Mars Sample Return

  2025-08-21

  articleOpen access

  Impact craters provide unique windows into deep subsurface habitability and early planetary processes that are otherwise inaccessible on Mars. The western rim of Jezero Crater is the in situ exploration target of the Perseverance rover, thus the formation dynamics and compositional context of these rim materials require further investigation. Using remote sensing data from Mars Reconnaissance Orbiter, we identify three distinct mineralogical units: low-calcium pyroxene, olivine, and Fe/Mg phyllosilicates mixed within the Jezero rim. Primary igneous phases alongside aqueously altered materials suggest preservation of pre-impact target lithologies reflecting regional geology. Our iSALE-2D impact simulations demonstrate that the outer wall rim materials originated from shallow depths (<0.75 km) and experienced minimal shock conditions (<2 GPa, <400 K), capable of preserving the original target minerals. Therefore, the rocks in the Jezero rim are a high-priority target for Mars Sample Return, offering pristine records of ancient Noachian Mars.

  PublisherOA PDFDOI

• Development and Evolution of Icy Layer Outcrops on Mars' North Polar Ice Cap: Observations of Vertical and Lateral Variability

  Journal of Geophysical Research Planets · 2025-01-01 · 1 citations

  articleOpen accessSenior author

  Abstract Mars' north polar ice cap features troughs that cut into the ice, exposing subsurface layers of different brightness and topographic expression. Specifically, these layers represent two different stratum types: lower albedo (higher dust content) marker beds, which protrude out of the wall topographically, and higher albedo (i.e., icier) interbeds, which are recessed compared to the marker beds. Here, we investigate the role of local‐scale processes by performing a detailed geomorphic characterization of variability in these strata across two sites, using a novel approach to calculating true layer protrusion which utilizes data from high‐resolution Digital Terrain Models. We measure protrusions of the order of meters but find lateral variations within a single trough exposure, suggesting a role for local‐scale processes in the evolution of the layers. We find that the topographic relief of protruding marker beds decreases as a function of decreasing trough slope and brightness (a proxy for dust cover/content). We also observe the presence of an insulative allochthonous dust veneer present on discrete sections of the trough wall, which we suspect plays an important role in modulating ice loss from the trough walls. A companion paper (Bramson et al., 2025, https://doi.org/10.1029/2024JE008360 ) models the contribution of insolation‐induced sublimation to present a new framework, and potential timescales for the development of the marker bed protrusion observed here.

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• Detection of ferrihydrite in Martian red dust records ancient cold and wet conditions on Mars

  Nature Communications · 2025-02-25 · 17 citations

  articleOpen access

  Abstract Iron oxide-hydroxide minerals in Martian dust provide crucial insights into Mars’ past climate and habitability. Previous studies attributed Mars’ red color to anhydrous hematite formed through recent weathering. Here, we show that poorly crystalline ferrihydrite (Fe 5 O 8 H · nH 2 O) is the dominant iron oxide-bearing phase in Martian dust, based on combined analyses of orbital, in-situ, and laboratory visible near-infrared spectra. Spectroscopic analyses indicate that a hyperfine mixture of ferrihydrite, basalt and sulfate best matches Martian dust observations. Through laboratory experiments and kinetic calculations, we demonstrate that ferrihydrite remains stable under present-day Martian conditions, preserving its poorly crystalline structure. The persistence of ferrihydrite suggests it formed during a cold, wet period on early Mars under oxidative conditions, followed by a transition to the current hyper-arid environment. This finding challenges previous models of continuous dry oxidation and indicates that ancient Mars experienced aqueous alteration before transitioning to its current desert state.

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• Spectral hydration features in nominally anhydrous minerals & implications for lunar remote sensing

  Icarus · 2025-05-12 · 1 citations

  articleOpen access

  The contributions of external and internal hydration (OH and H 2 O) on the shape and strength of hydration related features at 3 and 6 μm for lunar relevant nominally anhydrous minerals were investigated under vacuum conditions. Understanding the effect of hydration on the reflectance spectra of lunar analog materials in the laboratory can provide insights into remote sensing observations of the lunar surface and the potential for 3 and/or 6 μm observations to determine the speciation of hydration on the Moon. We demonstrate changes in the shape and strength of the broad 3 μm absorption feature in olivine and anorthite that is associated with the removal of hydration under changing environmental conditions. The overlapping nature of OH and H 2 O related absorption features in the ~3 μm region makes it difficult to uniquely determine the speciation of hydration. Despite evidence of H 2 O loss in the 3 μm region, we do not observe the fundamental bending mode of H 2 O at 6 μm, posing potential challenges for the detection H 2 O on the lunar surface and throughout our solar system. • Reflectance spectra of olivine and anorthite under ambient and vacuum conditions. • Changes in 3 μm absorption with the removal of internal and external hydration. • Unable to resolve the 6 μm fundamental bending mode of H 2 O in terrestrial samples.

  PublisherDOI

• Development and Evolution of Icy Layer Outcrops on Mars' North Polar Ice Cap: A Sublimation‐Based Framework

  Journal of Geophysical Research Planets · 2025-01-01 · 3 citations

  articleOpen accessSenior author

  Abstract Troughs carved into Mars' polar ice cap expose layers of different brightness and topography. These layers can be divided into two strata types: darker, higher dust content marker beds and brighter, lower dust content interbeds. In a companion paper (Pascuzzo et al., 2025, https://doi.org/10.1029/2024JE008377 ), we measure the topographic protrusion of the marker beds and interbeds. Here, we investigate processes and factors that contribute to the evolution of these layers to gain insight into the sublimation rates and timescales for active trough wall retreat, specifically the development of observed layer topography. We perform thermal modeling and ice sublimation calculations to explain the topography and its lateral variations. We use our results to develop a novel sublimation‐based framework for the development of marker bed protrusion. Our results suggest that marker beds can develop the observed meter‐scale protrusions in thousands of years via cyclical bursts of differential sublimation modulated by lag production and removal. We find that marker bed topography can easily be formed within a single period of high insolation driven by Mars' axial precession. If the present‐day topographic signatures of exposed trough strata are driven strictly by the differential sublimation and lag processes proposed here, our results suggest that ice retreat may have occurred ∼60–125 kya, with the topographic relief forming in 1–20 kyr. These results also lead us to suggest that thick insulative allochthonous dust veneers (such as that observed in Pascuzzo et al. (2025, https://doi.org/10.1029/2024JE008377 )) may play an important role in forcing hiatuses in trough wall retreat during high insolation periods.

  PublisherOA PDFDOI

• Variations in surface adsorbed H2O on lunar soils and relevant minerals

  Icarus · 2024-01-04 · 10 citations

  articleOpen access

  Spectral variations due to the removal of surface adsorbed H2O at 3 and 6 μm in reflectance spectra on lunar soils and relevant minerals (olivine, pyroxene, and plagioclase) have been assessed. This study characterizes variations in hydration features as a function of lunar relevant surface temperatures, to further understand current (i.e., M3, HRI-IR, VIMS) and future (i.e., Lunar Trailblazer) observations of diurnal changes in surface hydration. Additionally, we explore the utility of using the 6 μm H2O feature to discern the speciation of surface hydration at 3 μm. We perform controlled temperature measurements (25–200 °C) in a Linkam THMS600 Environmental Stage fixed to a Bruker LUMOS Microscope Fourier Transform IR (μFTIR) spectrometer. We observe clear and systematic changes in the strength of the 3 μm H2O/OH feature associated with the thermal removal of adsorbed H2O, in addition to changes in the overall shape and band position of the feature in both the terrestrial and lunar samples. The strength of the 3 μm feature for the compositionally distinct and relatively brighter Apollo highland soil (62231) is stronger and more symmetric than the 3 μm feature observed for the darker mare soil (10084). While several silicate related absorption features are identified near 6 μm, neither a distinguishable hydration feature nor any changes in reflectance that could be attributed to the presence or a change in the amount of surface adsorbed H2O were observed at 6 μm.

  PublisherDOI

• Signal to Noise Ratio and Spectral Sampling Constraints on Olivine Detection and Compositional Determination in the Intermediate Infrared Region: Applications in Planetary Sciences

  Earth and Space Science · 2024-08-01 · 1 citations

  articleOpen accessSenior author

  Abstract Spectral features of olivine across the intermediate infrared region (IMIR, 4–8 μm) shift systematically with iron‐magnesium content, enabling determination of olivine composition. Previous IMIR studies have used laboratory data with signal‐to‐noise ratios (SNRs) and spectral resolutions potentially greater than those of data derived from planetary missions. Here we employ a feature fitting algorithm to quantitatively assess the influence of data quality on olivine detection and compositional interpretation from IMIR data of 29 spectra of pure olivine of synthetic, terrestrial, lunar, and Martian origins, as well as 5 spectra of lunar pyroclastic beads measured as bulk samples. First, we demonstrate the effectiveness of the feature fitting algorithm in the interpretation of IMIR olivine spectra, predicting olivine composition with an average error of 6.4 mol% forsterite across all test spectra using laboratory‐quality data. We then extend this analysis to degraded test spectra with reduced SNRs and sampling rates and find a range of data qualities required to predict olivine composition within ±11 Mg# (molar Mg/[Mg + Fe] × 100) for the test spectra explored here. Spectra for the sample most relevant to lunar exploration, an Apollo 74002 drive tube consisting of microcrystalline olivine and glass‐rich pyroclastics, required SNRs ≥ 200 for sampling rates ≤25 nm to predict composition within ±11 Mg# of the sample's true composition. Derived limits on SNRs and sampling rates will serve as valuable inputs for the development of IMIR spectrometers, enabling comprehensive knowledge of olivine composition on the lunar surface.

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Frequent coauthors

• F. Poulet

  Université Paris-Saclay

  341 shared

• S. L. Murchie

  273 shared

• Jean‐Pierre Bibring

  Institut d'Astrophysique Spatiale

  243 shared

• N. Mangold

  Laboratoire de Planétologie et Géosciences

  214 shared

• B. L. Ehlmann

  California Institute of Technology

  210 shared

• B. Gondet

  Institut d'Astrophysique Spatiale

  198 shared

• R. E. Milliken

  186 shared

• A. Gendrin

  Schlumberger (British Virgin Islands)

  176 shared