About

Stephen Parman is a professor in the Department of Earth, Environmental & Planetary Sciences at Brown University. His research focuses on the chemical evolution of the Earth, moons, and planets. His work encompasses geochemistry, Earth history, tectonics, volcanology and petrology, and planetary geoscience. Parman is involved in studying the processes that shape planetary bodies and their chemical compositions, contributing to our understanding of planetary formation and evolution. Recent notable research includes a study published in Icarus examining lunar volcanic gas cloud chemistry through the analysis of glass bead surface sublimates from the Apollo mission, which suggests a change in eruption style over the course of a pyroclastic volcanic eruption in the Taurus-Littrow Valley. Additionally, he has engaged in discussions about innovative space exploration concepts, such as a Mercury Scout mission utilizing solar sails, and has been part of a Brown-led team selected by NASA to study the Moon with the goal of establishing a permanent lunar base. Parman's work integrates advanced analytical techniques and collaborative efforts to explore planetary processes and contribute to space exploration initiatives.

Research topics

• Geology
• Geochemistry
• Astrobiology
• Mineralogy
• Earth science

Selected publications

• Constraints on Noble Gas Variability in OIB and MORB From Non‐Equilibrium Magmatic Degassing Models

  Geochemistry Geophysics Geosystems · 2026-03-01

  articleOpen access

  Abstract Noble gas concentrations in ocean island basalts (OIB) and mid‐ocean ridge basalts (MORB) are affected by degassing processes, obscuring their pre‐eruptive characteristics. Degassing corrections commonly assume near‐equilibrium partitioning of noble gases between melt and vapor. However, kinetic disequilibrium has been proposed as a mechanism capable of modifying noble gas ratios. For example, kinetic effects may allow OIBs to exhibit lower 3 He contents than MORBs, even if OIB plumes sample a low 4 He/ 3 He “undegassed” primordial lower mantle—the so‐called “Helium Paradox” (Gonnermann & Mukhopadhyay, 2007, https://doi.org/10.1038/nature06240 ). It has also been suggested that kinetic effects allow OIB and MORB to share a homogeneous pre‐degassing 3 He/ 22 Ne ratio. Despite this, inferred mantle compositions may not require the presence of an “undegassed” reservoir, and there is evidence that OIB and MORB sources exhibit heterogenous 3 He/ 22 Ne ratios. Here, we model the kinetics of and noble gas exchange between bubbles and melt within a three‐stage framework for magmatic ascent to evaluate the magnitude of non‐equilibrium fractionation. The first and third stages treat the kinetics of bubble growth during closed‐system decompression, whilst the second treats gas exchange between ascending bubbles and a melt at rest within a shallow, open‐system, sub‐volcanic reservoir. Across plausible ranges of ascent rate, bubble populations, and noble gas diffusivity, our results indicate that disequilibrium cannot produce variations in 3 He contents and 3 He/ 22 Ne ratios sufficient to reproduce the range observed in OIB and MORB. Therefore, OIB and MORB sources cannot share a homogenous 3 He/ 22 Ne ratio, and disequilibrium does not resolve the “Helium Paradox.”

  PublisherDOI

• LunaSCOPE: Exploration Science Approaches To Constraining Lunar Surface Properties for Sustained Surface Operations

  2026-01-01

  articleOpen access
  PublisherDOI

• Thermal Evolution of the Moon Dominated by the Earth

  Zenodo (CERN European Organization for Nuclear Research) · 2025-07-23

  articleOpen accessSenior author
  PublisherDOI

• Thermal Evolution of the Moon Dominated by the Earth

  Zenodo (CERN European Organization for Nuclear Research) · 2025-07-23

  articleOpen accessSenior author
  PublisherDOI

• Tidal Heating of the Lunar Magma Ocean: Reconciling an Old Moon with a Young Solidification

  arXiv (Cornell University) · 2025-11-25

  preprintOpen access

  The timing of the Moon's formation is fundamental to understanding the early Earth-Moon system. Ages of lunar magma ocean (LMO) crystallization have long been regarded as a key proxy for that event. Yet returned lunar sample ages cluster near the relatively young age of ~4.35 billion years ago (Ga). These ages are commonly interpreted as recording either a young-Moon formation age or later thermal resetting. Here we show that, for an old Moon (>4.5 Ga), the ~4.35 Ga age cluster can instead arise naturally from early LMO thermal evolution under Earth's tidal forcing. We identify tidal heating within a partially molten LMO as a major internal heat source. It offsets much of the early heat loss and maintains a long-lived high-energy state for >150 million years. As crystallization proceeded, this stable state was ultimately lost through the rapid collapse of tidal heating. The last stages of LMO solidification were compressed into a short interval near ~4.35 Ga. The tidal heat source decouples Moon formation from final LMO solidification. As an outcome of LMO evolution, we predict asymmetric late-stage crystallization between the lunar nearside and farside, potentially linking tidally modulated LMO evolution to the long-term lunar dichotomy.

  PublisherOA PDFDOI

• Lunar volcanic gas cloud chemistry: Constraints from glass bead surface sublimates

  Icarus · 2025-04-24 · 3 citations

  articleOpen access

  Lunar pyroclastic glass beads preserve a record of physical and chemical conditions within volcanic gas clouds in the form of nanoscale minerals vapour-deposited onto their surfaces. However, the scale of these mineral deposits - less than 100 nm - has presented challenges for detailed analysis. Using SEM, TEM, APT, and NanoSIMS, we analysed pristine black glass beads from Apollo drive tube 74001 and found a sequence of sulfide deposition that directly evidences lunar gas cloud evolution. The deposits are predominantly micromound structures of nanopolycrystalline sphalerite ((Zn,Fe)S), with iron enrichment at the bead-micromound interface. Thermochemical modelling indicates that hydrogen and sulfur were major elements within the volcanic plume and ties the iron gradient to decreasing gas pressure during deposition. This pressure drop may also be consistent with our observed trend of potential δ 34 S depletion. Finally, Apollo 17 74220 orange beads, deposited higher in the Shorty Crater sequence, appear to lack abundant ZnS nanocrystals ( Liu and Ma, 2024a ), suggesting a change in vapour deposition between orange- and black-glass bead deposition. Together, our results suggest a change in eruption style over the course of a pyroclastic volcanic eruption in the Taurus-Littrow Valley. • Pristine 74,001 lunar glass bead surfaces host diverse vapour-deposited nanominerals. • The deposits primarily consist of nanopolycrystalline sphalerite ((Zn,Fe)S). • Thermochemical modelling supports current lunar volcanic gas composition estimates.

  PublisherDOI

• The bulk composition and initial size of Mercury

  Icarus · 2025-05-22 · 1 citations

  articleOpen accessSenior author

  Enstatite chondrites are often used as models for the bulk composition of Mercury because they have similarly low oxygen fugacities. However, e-chondrites are too Si-rich to explain the observed composition of Mercury's lavas. Here we explore a model in which an initially enstatite chondrite-like Mercurian silicate magma ocean loses Si to the large Fe core during early differentiation. We define a Mercury Fractionation Line (MFL) based on average basaltic geochemical terrane compositions and assume Mercury's bulk silicate composition must fall along this line. We estimate that 26.5–36.7 ± 7.5 % (1σ) Si must be lost from an initial mantle to bring the e-chondrite compositions up to the MFL. Assuming that the Si is partitioned into the core, this implies a core Si content of 2.8–3.9 ± 0.8 wt% and an oxygen fugacity of IW–4.5 ± 1.0. We also show that a model where Mercury was initially ~2 times larger is consistent with more reducing oxygen fugacities (IW–5.0 ± 1.0) and a higher core Si content (~15 wt%). This estimated initial Mercury size is also consistent with predictions from dynamical simulations. We consider how Si partitioning into the core affects the δ 30 Si composition of the mantle. Though uncertainties are large, we show that as the initial radius of Mercury increases, δ 30 Si decreases, trending towards the δ 30 Si composition of enstatite chondrites. Our calculations do not constrain the mechanism by which Mercury's mantle may have been lost. However, if they are correct, they imply that the mantle loss must have happened after core formation. • Mercury's mantle likely lost silicon to the core during formation. • Mercury may have formed larger and more reduced than its present-day size. • A larger, reduced Mercury is consistent with a silicon-rich core.

  PublisherDOI

• Comparative Petrologic Analysis of Potential Noritic Diogenites to Yamato Type B Diogenites

  Abstracts with programs - Geological Society of America · 2025-01-01

  article
  PublisherDOI

• An oxygen fugacity-temperature-pressure-composition model for sulfide speciation in Mercurian magmas

  Geochimica et Cosmochimica Acta · 2024-11-19 · 8 citations

  articleOpen access

  The NASA MESSENGER mission revealed that lavas on Mercury are enriched in sulfur (1.5–4 wt%) compared with other terrestrial planets (<0.1 wt%) due to high S solubility in silicate melt under its very low oxygen fugacity (ƒO 2 ). However, the speciation of that S remains poorly constrained. In this study, we evaluate the role of pressure, temperature, and melt composition on S solubility and speciation in reduced magmas relevant to Mercury. Sulfur speciation was determined by S K-edge XANES spectra collected in 60 experiments that span a range of pressure (0.1 to 5 GPa), temperature (1225 to 1850 °C), and ƒO 2 (IW-0.8 to IW-8.6). Data were analysed using new relevant XANES standards and XANES spectral unmixing techniques. Stepwise forward regression was used to develop empirical equations for S species (MgS, CaS, and TiS). We found that f O 2 , P/T, and S content in the silicate melt at sulfide saturation (SCSS) exert the main controls on MgS content (wt.%) in the silicate melt, and that f O 2 and MgS content in the silicate melt exert the main controls on SCSS. MgS liq w t . % = a + bP T + c log fO 2 + d [ S w t . % ] SCSS (1) We find that as ƒO 2 decreases from IW-2 to IW-7, S speciation in silicate melt goes through two major changes. Between IW-2 and IW-4, FeS and FeCr 2 S 4 species are destabilized, and CaS becomes the dominant S species with minor TiS. Below IW-4, MgS is the dominant S species with minor CaS. At low f O 2 , S bonding with Fe, Mg, Ca, Ti, Na, and Mn affect the activities of SiO 2 , MgO, CaO, TiO, Na 2 O, and MnO in the silicate melt. This stabilizes enstatite at the expense of forsterite, destabilizes the Ca-bearing minerals plagioclase and clinopyroxene, and shifts plagioclase chemistry from the Ca-rich endmember anorthite to the Na-rich endmember albite as understand by reprojecting silicate ternary diagrams incorporating S speciation data. At the expense of MgS, CaS is more stable in the silicate melt at higher pressures at f O 2 below IW-4 creating a pathway for CaS to be carried in the silicate melt from depth to the surface before oldhamite (CaS) crystallization. These S speciation changes have substantial impacts on physicochemical properties of silicate melt such as viscosity, melting temperature, and mineral stability, which led to the distinct evolution of Mercury and other reduced planetary interiors.

  PublisherDOI

• Thank You to Our 2021 Peer Reviewers

  Journal of Geophysical Research Solid Earth · 2022-04-01

  articleOpen access

  Abstract Editors of JGR‐Solid Earth express their appreciation to those who served as peer reviewers for the journal in 2021.

  PublisherOA PDFDOI

Recent grants

• Experimental Study of Noble Gas Behavior in the Mantle

  NSF · $350k · 2010–2014

• Recycling of Noble Gases in Ring-bearing Silicates

  NSF · $300k · 2014–2018

Frequent coauthors

• R. F. Cooper

  Providence College

  45 shared

• C. Jackson

  Tulane University

  43 shared

• B. A. Anzures

  Johnson Space Center

  40 shared

• T. C. Prissel

  Johnson Space Center

  25 shared

• E. M. Parmentier

  Brown University

  25 shared

• J. W. Head

  Brown University

  24 shared

• T. L. Grove

  24 shared

• C. M. Pieters

  19 shared