About

Ananya Mallik is an Assistant Professor at the Department of Geosciences at the University of Arizona. She holds the Endowed Chair in The RealReal, Inc. and is the Principal Investigator of the Experimental Petrology Laboratory. Her research interests include subduction zone magmatism, deep Earth volatile cycling, surface-interior exchange on Earth and other terrestrial planetary bodies, planetary interior evolution, and crust formation. She has received notable awards such as the 2025 National Science Foundation CAREER Award, the 2022-2023 Mineralogical Society of America Distinguished Lecturer, and the 2015 Alexander von Humboldt Postdoctoral Fellowship in Germany.

Research topics

• Geology
• Geochemistry
• Petrology
• Geophysics
• Mineralogy
• Ecology
• Physics
• Paleontology
• Chemistry
• Environmental chemistry
• Biology
• Chromatography

Selected publications

• Microstructural Analysis of Lunar Dunite Clast from Meteorite NWA 11421 and Physical Constraints on Excavation of Upper Lunar Mantle Material.

  2026-02-04

  articleOpen access

  The lunar dunite clast, D1, from meteorite NWA 11421 represents the first sample that can be reliably traced to the lunar mantle and promises to provide new insights into the Moon’s interior structure and chemistry. We conducted electron backscatter diffraction (EBSD) analysis of the mantle clast to characterize olivine microstructures and to quantify its shock and thermal histories. The EBSD data indicate that D1 experienced a high-pressure, low-temperature shock event. Grain orientation spread (GOS) indicates a weighted shock stage (WSS) of 4.1 ± 1.3, corresponding to shock pressures between 15 and 20 GPa. Crystal rotation axis orientations associated with low-angle (2–10°) misorientations demonstrate preferential activation of C-type slip systems, consistent with relatively low shock temperatures of 723 ± 99 °C. Noticeably, this shock temperature estimate is below the sample’s equilibrium temperature of 980 ± 20 °C determined by Ca-in-pyroxene thermobarometry. This temperature contrast suggests that the thermal state achieved during shock was conducive to preserving the primary trace element signature of the mantle. The olivine within D1 displays a weak B-type crystallographic preferred orientation with a low M-index consistent with shock deformation when compared to various terrestrial mantle xenoliths. Combined with the sample’s depth of origin, these characteristics suggest D1 might have been launched from the Imbrium or Serenitatis basins and may provide the first direct chemical constraints on nearside lunar mantle.

  PublisherOA PDFDOI

• Thin H ₂ -dominated Atmospheres as Signposts of Magmatic Outgassing on Tidally Heated Terrestrial Exoplanets

  The Planetary Science Journal · 2026-04-01

  articleOpen accessSenior author

  Abstract H 2 -dominated terrestrial exoplanets are highly accessible to atmospheric characterization via transmission spectroscopy, but such atmospheres are generally thought to be unstable to escape. Here, we propose that close-in, eccentric terrestrial exoplanets can sustain H 2 -dominated atmospheres due to intense tidally driven volcanic degassing. We develop an interior–atmosphere framework to assess whether volcanic outgassing can sustain H 2 -dominated atmospheres over geologic timescales (≥1 Gyr). We incorporate interior redox state, tidal heating, volatile inventory, and planetary parameters to compute outgassing fluxes and confront them with energy-limited hydrodynamic escape. We demonstrate that to sustain an H 2 -dominated atmosphere, a terrestrial exoplanet must have a water-rich mantle and reduced melt, in addition to high eccentricity. We additionally demonstrate that detection of a specifically thin H 2 -dominated atmosphere is a sign of current magmatic outgassing. We delineate an “outgassing zone” (OZ) most favorable to the existence of such planets, and identify the most observationally compelling targets. We propose combining precise mass–radius–eccentricity measurements with JWST constraints on atmospheric mean molecular mass μ to search for thin H 2 -dominated atmospheres. Inversely, we argue that robust atmospheric nondetections on OZ exoplanets can constrain the planetary interior, including melt redox state, mantle melt fraction, volatile inventory, and tidal heat flux.

  PublisherDOI

• The South Pole-Aitken basin constrains the early evolution and differentiation of the Moon

  2026-03-14

  articleOpen access

  The South Pole-Aitken basin (SPA) is the oldest and largest known impact basin on the Moon. We use gravity, topography, and surface remote sensing data together with impact simulations to reveal new details of the structure and formation of the basin and to place new constraints on the structure, differentiation, and early evolution of the Moon. The geophysical expression of SPA reveals an elongated, tapered basin formed in a southward-directed oblique impact. Impact simulations show that the downrange excavation from the core of a differentiated impactor can explain the tapered shape of the basin. Remote sensing reveals an asymmetric ejecta blanket rich in thorium, consistent with asymmetric excavation of late-stage lunar magma ocean liquids enriched in incompatible elements such as potassium, rare earth elements, and phosphorus (KREEP). The distribution of Th-rich ejecta can be explained in the context of models of magma ocean crystallization, in which progressive solidification of the magma ocean caused it to become concentrated beneath regions of thinner crust, eventually pinching out to zero thickness beneath the farside highlands and finally concentrating within the nearside Procellarum KREEP terrane. At an intermediate stage, a thin and discontinuous layer of late-stage magma ocean liquids would have been present beneath the southwestern half of the basin extending onto the nearside, which explains the observed distribution of Th-rich SPA ejecta. Material excavated by SPA on the farside and the younger Imbrium basin on the nearside reveal the evolution of the late-stage magma ocean products in space and time. The ages of these basins and Th concentrations of their ejecta match the modeled compositional evolution of the magma ocean. Thus, the ejecta of SPA provides a means to sample the late-stage magma ocean as well as the lunar mantle. High-resolution gravity data reveals an annulus of large-amplitude, short-wavelength gravity anomalies surrounding the basin, consistent with the predicted distribution of material excavated from the lunar mantle. Remote sensing observations of craters excavating into this material indicate a heterogeneous mantle at the time of impact, containing both orthopyroxene-rich and clinopyroxene-rich material. Experimental work predicts that these distinct compositions should form early and late in the magma ocean crystallization sequence, respectively. Thus, the observed compositions are consistent with partial or ongoing overturn of the lunar mantle at the time of the SPA impact. Together, these analyses show how the Moon’s oldest known impact basin provides a key constraint on the interior structure, differentiation, and early evolution of the Moon. This work provides context for recent, ongoing, and future missions exploring the lunar farside that offer the opportunity for in situ exploration of materials derived from the SPA impact.

  PublisherDOI

• Nitrogen mineral hosts in subduction zone metamorphosed ultramafic rocks: Implications for deep Forearc (to Subarc) transfer

  Chemical Geology · 2026-02-16

  articleOpen access

  Subduction of serpentinized mantle lithosphere delivers nitrogen (N) into the mantle, but the residency and speciation of N therein remain largely unknown. Serpentine, talc, and chlorite have been proposed as likely hosts in K-poor ultramafic rocks due to the minerals' sheet-like structures and the ability for N to reside in interlayer sites. In this study, we explore whether these three minerals are the primary hosts of N in subduction-related mantle lithosphere and metasomatized hybrid rocks (serpentinites, talc schists, and chlorite schists) by analyzing the N concentrations and isotope compositions of paired whole-rock and phyllosilicate mineral separates. Mineralogy of nine samples and sixteen mineral separates from ultramafic units in Syros, Greece, and Pam Peninsula, New Caledonia, were characterized by petrography and X-ray diffraction (XRD) prior to N analyses. Whole-rock N concentrations are from 25 to 102 μg/g and N-isotopes compositions ( δ 15 N air ) range from −0.2 to +6.9‰, whereas mineral separates contain 8 μg/g to 176 μg/g N with δ 15 N of −1.2 to +7.0‰. These results show that ultramafic rocks and phyllosilicate minerals from subduction zone settings contain 10's to 100's of μg/g of N, and have δ 15 N consistent with mixing with a sedimentary-derived fluid. However, mineral separates show variable N and δ 15 N enrichment or depletion relative to their respective whole-rocks, with most separates containing ≤40% of the whole-rock N and systematically lower δ 15 N values. These data indicate that, for the majority of the samples, a considerable fraction of the N is hosted in minerals or sites within the whole-rock not captured in the mineral separates. We combine textural observations and geochemical correlations to propose that the discrepancy between the whole-rocks and their mineral separates can be explained by heterogeneous N distribution among different generations of phyllosilicate minerals within single samples and/or significant N hosted in other minerals and sites (e.g., accessory phases or interstitial phases). Further investigation is required to distinguish between these possibilities, with implications for N speciation and stability during subduction zone metamorphism from the forearc to depths beneath arcs and beyond. • Rock and mineral N concentrations are from 8 to 172 μg/g and δ 15 N from −1.2 to +7.0‰. • Phyllosilicate minerals alone cannot account for whole-rock N-budget in most cases. • Nitrogen composition of the same phyllosilicate mineral may vary by generation and texture. • Nitrogen may reside in accessory phases, complicating N mobility during subduction. • Significant amounts of N could be subducted in such rocks to deep forearcs and beyond.

  PublisherDOI

• Southward impact excavated magma ocean at the lunar South Pole–Aitken basin

  Nature · 2025-10-08 · 3 citations

  articleOpen access

  Abstract The ancient South Pole–Aitken impact basin provides a key data point for our understanding of the evolution of the Moon, as it formed during the earliest pre-Nectarian epoch of lunar history 1 , excavated more deeply than any other known impact basin 2,3 and is found on the lunar far side, about which less is known than the well-explored near side. Here we show that the tapering of the basin outline and the more gradual topographic and crustal thickness transition towards the south support a southward impact trajectory, opposite of that commonly assumed. A broad thorium-rich and iron-rich ejecta deposit southwest of the basin is consistent with partial excavation of late-stage magma ocean liquids. These observations indicate that thorium-rich magma ocean liquids persisted only beneath the southwestern half of the basin at the time of impact, matching predictions for the transition from a global magma ocean to a local enrichment of potassium, rare-earth elements and phosphorus (KREEP) in the near-side Procellarum KREEP Terrane. These results have important implications for the upcoming human exploration of the lunar south pole by Artemis, as proposed landing sites are now recognized to sit on the downrange rim and thorium-rich impact ejecta of the basin.

  PublisherOA PDFDOI

• Trace Element Analyses of Plagioclase from Troctolite 76535 and Implications for Mg-suite Petrogenesis

  2025-01-21

  preprint

  Certain Mg-suite samples display enrichment in incompatible elements, likely resulting from the assimilation of the material that crystallized at the very late stages of magma ocean (ur-KREEP). This study uses trace element analyses of plagioclase separates from sample 76535 to estimate the Rare Earth Element (REE) concentration of the Mg-suite parental liquid and assess the extent of contribution from ur-KREEP. Thirty-three trace elements, including REEs, were measured in the separates and the measured REEs reflect magmatic conditions being free from subsolidus alteration. The Mg-suite parental liquid was estimated using these REE data as targets for a Python-based forward model which employs a RhyoliteMELTS-defined liquid line of descent. The estimated parental liquid shows REE enrichments of 200 times chondritic levels for Light REEs and 20 times for Heavy REEs. Mixing models between the REE compositions of a potential Mg-suite primary liquid and modeled ur-KREEP indicate that 30-50% assimilation of ur-KREEP is required to reproduce the observed REE concentrations in the Mg-suite parental liquid. We demonstrate an approach to determine the petrogenesis of a sample by characterizing a very limited quantity of grains, in an effort to maximize the scientific output from current and future returned samples such as Artemis.

  PublisherDOI

• Thin H$_2$-dominated Atmospheres as Signposts of Magmatic Outgassing on Tidally-Heated Terrestrial Exoplanets

  ArXiv.org · 2025-10-08

  preprintOpen accessSenior author

  H$_2$-dominated terrestrial exoplanets are highly accessible to atmospheric characterization via transmission spectroscopy, but such atmospheres are generally thought to be unstable to escape. Here, we propose that close-in, eccentric terrestrial exoplanets can sustain H$_2$-dominated atmospheres due to intense tidally-driven volcanic degassing. We develop an interior-atmosphere framework to assess whether volcanic outgassing can sustain \ch{H2}-dominated atmospheres over geologic timescales ($\geq$1 Gyr). We incorporate interior redox state, tidal heating, volatile inventory, and planetary parameters to compute outgassing fluxes and confront them with energy-limited hydrodynamic escape. We demonstrate that to sustain an H$_2$-dominated atmosphere, a terrestrial exoplanet must have a water-rich basal magma ocean and reduced melts, in addition to high eccentricity. We additionally demonstrate that detection of a specifically thin H$_2$-dominated atmosphere is a sign of current magmatic outgassing. We delineate an "outgassing zone" (OZ) most favorable to the existence of such planets, and identify the most observationally compelling targets. We propose combining precise mass-radius-eccentricity measurements with JWST constraints on atmospheric mean molecular mass $μ$ to search for thin H$_2$-dominated atmospheres. Inversely, we argue that robust atmospheric non-detections on OZ exoplanets can constrain the planetary interior, including melt redox state, mantle melt fraction and volatile inventory, and tidal heat flux.

  PublisherOA PDFDOI

• Nitrogen Sources and Mineral Hosts within Shallow Sedimentary Mélange Matrix: Insights from San Simeon, California

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

  article
  PublisherDOI

• Mass transfer from the slab to the mantle and implications for chemical geodynamics in subduction zones

  2025-01-01

  article1st authorCorresponding
  PublisherDOI

• Present-day Earth mantle structure set up by crustal pollution of the basal magma ocean

  Science Advances · 2025-07-18 · 11 citations

  articleOpen access

  The crystallization of a global magma ocean during early terrestrial planet evolution and the subsequent segregation of a longer-lived "basal magma ocean" (BMO) atop the core set up the evolution of the mantle-atmosphere system. Although seismic evidence for a BMO exists on present-day Mars and the Moon, the Earth's BMO is (near-)completely solidified. Seismically observed "large low-velocity provinces" (LLVPs) are thought to have resulted from the canonical "fractional" style of BMO crystallization. However, we show using thermodynamic modeling that BMO fractional crystallization yields lowermost-mantle densities much higher than those of LLVPs. In turn, pollution of the BMO by progressive addition of recycled basaltic crust and related "reactive crystallization" can reconcile LLVP volumes, densities, and compositions. This model also makes testable predictions of the compositions of "ultralow-velocity zones," enigmatic deep Earth seismic domains, and possible BMO remnants. The critical role of crustal pollution elucidates the survival of a BMO on Mars, but implies an Earth-like fate for any Venusian BMO.

  PublisherDOI

Recent grants

• Collaborative Research: Tracking nitrogen in mélange matrix from fore-arc to sub-arc depths with implications for deep nitrogen cycling: A combined field and experimental approach

  NSF · $338k · 2022–2025

Frequent coauthors

• Paul Bremner

  18 shared

• Rajdeep Dasgupta

  Rice University

  16 shared

• Matthew Diamond

  Arizona State University

  15 shared

• H. Fuqua Haviland

  12 shared

• J. M. Nelson

  Texas A&M University

  11 shared

• R. L. Hervig

  11 shared

• Emily H.G. Cooperdock

  9 shared

• Tyler J. Goepfert

  Arizona State University

  8 shared

Awards & honors

• 2025 - National Science Foundation CAREER Award
• 2022 - 2023 Mineralogical Society of America Distinguished L…
• 2015 - Alexander von Humboldt Postdoctoral Fellowship, Germa…