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Direct detection of hydrogen reveals a new macroscopic crustal water reservoir on early Mars

Estrid Buhl Naver, Katrine Wulff Nikolajsen, Martin Sæbye Carøe, Domenico Battaglia, Jens Frydenvang, Martin Bizzarro, Jakob Sauer Jørgensen, Kim Lefmann, Anders Kaestner, David Christian Mannes, Phil Cook, Henrik Birkedal, Thorbjørn Erik Køppen Christensen, Innokenty Kantor, Henning Friis Poulsen, Luise Theil Kuhn

TL;DR

This study demonstrates a non-destructive, three-dimensional workflow that combines neutron computed tomography, X-ray computed tomography, and X-ray diffraction tomography to map hydrogen distribution in Martian crustal material. Applying the method to the NWA 7034 meteorite, the authors identify hydrogen-rich Fe-oxyhydroxide clasts forming a macroscopic water reservoir, with up to $635 ext{ ppm H}_2 ext{O}$ contributing about $11\%$ of the meteorite’s total water, and suggest similar near-surface hydration on early Mars as evidenced by parallels with Jezero crater samples. The work provides direct, sample-wide hydrogen mapping and mineral context without destructive preparation, highlighting features that are likely widespread hydrous alteration on early Mars and establishing a paradigm for MSR sample early-stage characterization. Overall, the integrated NCT–XCT–XRD-CT approach enhances interpretation of Martian hydration, aids target prioritisation for MSR analyses, and substantiates the existence of a planetary-scale near-surface water reservoir in early Mars.

Abstract

The next great leap in Martian exploration will be the return of samples to Earth. To ensure the maximum scientific return from studying these samples, the development and utilisation of nondestructive analytical techniques are essential to enable early three-dimensional characterisation of their interiors. Neutron computed tomography is a powerful method in this context: it is highly sensitive to hydrogen and complements the more conventional X-ray computed tomography. Because the distribution and nature of hydrous phases are central to understanding the habitability, the climatic and geological evolution, and potential biosignatures of Mars, identifying hydrogenbearing phases in Martian crustal rocks is of particular importance. Using the only Martian crustal material available on Earth, the NWA 7034 meteorite and its pairs, we show that combined neutron and X-ray computed tomography enables non-destructive sample-wide mapping of hydrogen and reveals the distribution and petrographic contexts of hydrous phases. We identify hydrogen-rich iron oxyhydroxides within ancient igneous clasts, forming a macroscopic mineralogical water reservoir within the meteorite. These alteration assemblages closely resemble those observed in samples collected by the Perseverance rover in Jezero crater, where hydrated iron oxyhydroxides are also present. This similarity suggests that such phases may represent a widespread near-surface water reservoir on early Mars.

Direct detection of hydrogen reveals a new macroscopic crustal water reservoir on early Mars

TL;DR

This study demonstrates a non-destructive, three-dimensional workflow that combines neutron computed tomography, X-ray computed tomography, and X-ray diffraction tomography to map hydrogen distribution in Martian crustal material. Applying the method to the NWA 7034 meteorite, the authors identify hydrogen-rich Fe-oxyhydroxide clasts forming a macroscopic water reservoir, with up to contributing about of the meteorite’s total water, and suggest similar near-surface hydration on early Mars as evidenced by parallels with Jezero crater samples. The work provides direct, sample-wide hydrogen mapping and mineral context without destructive preparation, highlighting features that are likely widespread hydrous alteration on early Mars and establishing a paradigm for MSR sample early-stage characterization. Overall, the integrated NCT–XCT–XRD-CT approach enhances interpretation of Martian hydration, aids target prioritisation for MSR analyses, and substantiates the existence of a planetary-scale near-surface water reservoir in early Mars.

Abstract

The next great leap in Martian exploration will be the return of samples to Earth. To ensure the maximum scientific return from studying these samples, the development and utilisation of nondestructive analytical techniques are essential to enable early three-dimensional characterisation of their interiors. Neutron computed tomography is a powerful method in this context: it is highly sensitive to hydrogen and complements the more conventional X-ray computed tomography. Because the distribution and nature of hydrous phases are central to understanding the habitability, the climatic and geological evolution, and potential biosignatures of Mars, identifying hydrogenbearing phases in Martian crustal rocks is of particular importance. Using the only Martian crustal material available on Earth, the NWA 7034 meteorite and its pairs, we show that combined neutron and X-ray computed tomography enables non-destructive sample-wide mapping of hydrogen and reveals the distribution and petrographic contexts of hydrous phases. We identify hydrogen-rich iron oxyhydroxides within ancient igneous clasts, forming a macroscopic mineralogical water reservoir within the meteorite. These alteration assemblages closely resemble those observed in samples collected by the Perseverance rover in Jezero crater, where hydrated iron oxyhydroxides are also present. This similarity suggests that such phases may represent a widespread near-surface water reservoir on early Mars.
Paper Structure (13 sections, 2 equations, 5 figures, 2 tables)

This paper contains 13 sections, 2 equations, 5 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Results
  3. Discussion
  4. Methods
  5. Neutron and X-ray tomography
  6. X-ray diffraction tomography
  7. Attenuation calculations
  8. Acknowledgements
  9. Data availability
  10. Author contributions
  11. Supplementary
  12. S1 Rietveld refinement
  13. S2 Calculating attenuation values

Figures (5)

  • Figure 1: 3D rendering of meteorite and clasts. a) 3D rendering of the attenuation tomograms cut in half in $z$ to show two H-Fe-ox clasts, showing neutron attenuation on the left and X-ray attenuation on the right. White means high attenuation, dark means low attenuation. b) 3D rendering of segmented phases throughout the meteorite, with H-rich Fe-oxyhydroxides in blue and H-poor Fe-Ti oxides in red. c) 3D rendering of the three biggest H-Fe-ox clasts.
  • Figure 2: Close up view of H-Fe-Ox clasts and matrix. The rows show different contrasts and the columns show different areas in the meteorite. The contrasts are X-ray (XCT) and neutron (NCT) imaging in row 1 and 2, respectively, as well as the H-rich (blue) and Fe/Ti, H-poor (red) segmented phases from XCT and NCT downscaled to match XRD-CT resolution in row 3 and the SAXS (XRD-CT) signal (diffracted signal at scattering vector 0.1 Å$^{-1}$<Q<0.6 Å$^{-1}$) in row 4. All scale bars are 100 µ m.
  • Figure 3: Composition of H-Fe-ox clasts. Comparison between compositions of H-rich and H-poor areas in the H-Fe-Ox clasts based on Rietveld refinement of XRD-CT data. "Mag." represents magnetite/maghemite.
  • Figure S4: Rietveld refinement of H-rich phases in clast 1 performed in Maud. Vertical dashed line indicate Q-range used for Rietveld refinement. Q-range used to determine SAXS signal labelled.
  • Figure S5: Rietveld refinement of H-rich phases in clast 3 performed in Maud. Vertical dashed line indicate Q-range used for Rietveld refinement. Q-range used to determine SAXS signal labelled.