^1,2,3Xhonatan Shehaj,²Eleonora Ammannito,^3,4Giovanni Pratesi
Meteoritics & Planetary Sciences (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70112]
¹Dipartimento di Fisica, Universit`a degli Studi di Trento, Trento, Italy
<sup>2</sup>Agenzia Spaziale Italiana, Rome, Italy
<sup>3</sup>Dipartimento di Scienze della Terra, Universit`a degli Studi di Firenze, Florence, Italy
⁴Istituto di Geoscienze e Georisorse—IGG-CNR, Pisa, Italy
Published by arrangement with John Wiley & Sons

In Earth’s igneous systems, crystal mushes, crystal-rich frameworks permeated by silicate melt, represent a common and fundamental stage in the evolution of magma bodies. However, whether crystal mushes occur within Martian igneous systems and play a comparable role is unknown. Here, we present a comprehensive petrography and mineral chemistry study of a new pyroxene- and olivine-phyric shergottite, Northeast Africa 053, found in Libya in 2023. This sample exhibits a basaltic bulk chemical composition and a porphyritic texture, primarily characterized by pyroxene and olivine megacrysts set in a groundmass of lath-like maskelynite (shocked plagioclase) and pyroxene. A remarkable feature of this sample is the distribution of pyroxene crystals, which delineates a distinct fine-grained layering juxtaposed within a coarse-grained domain, unusual for a Martian meteorite. Pyroxene grains in both textural domains exhibit a consistent zoning pattern, typically characterized by Mg-rich pigeonite cores, augite mantles, and in some grains, a defined Fe-rich pigeonite rims. High-precision electron microprobe analyses reveal that distinct chemical differences evolved during the late stages of pyroxene crystallization, particularly in the FeO content of the crystal rims and in groundmass grains between the two textural domains. In the fine-grained layer, late-forming pyroxene shows a progressive FeO enrichment from rims to groundmass (FeOrim = 27.72 ± 3.73 wt%; FeOgroundmass = 30.30 ± 2.15 wt%), whereas in the coarse-grained domain, the FeO content is lower (FeOrim = 25.68 ± 5.74 wt%; FeOgroundmass = 26.90 ± 5.19 wt%). This trend, along with the juxtaposition of the fine- and coarse-grained texture, suggests that the two textural domains likely formed in separate zones within a single evolving magmatic body, shaped by local thermal gradients. We interpret these features as relicts of a dynamic crystal mush system, potentially driven by magma ascent and shallow emplacement. This implies that Martian magmatic activity exhibited rheological properties and dynamics similar to those observed in Earth’s magmatic systems, highlighting the complex internal architecture of Martian igneous bodies.

¹Ingo Leya
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70118]
¹Space Science and Planetology, University of Bern, Bern, Switzerland
Published by arrangement with John Wiley & Sons

Production rates for the cosmogenic radionuclides 10Be, 14C, 26Al, 36Cl, 41Ca, 53Mn, and 60Fe in a large variety of meteorites, that is, ordinary chondrites (H, L, LL), carbonaceous chondrites, HED meteorites, ureilites, Martian meteorites, and iron meteorites and in the uppermost ~2 m of the lunar surface are modeled. The new model, which covers a wide range of pre-atmospheric radii and shielding conditions, is the first version to fully implement primary and secondary α-particles. Additionally, the new model gives for the first time uncertainties that are calculated using the same type of modeling as the production rates; they are therefore no longer best guesses. A series of tests demonstrate that the assumption of a spherical geometry has only little effect on the modeled production rate, as long as the irradiation is isotropic, and that all types of carbonaceous chondrites can be described using one set of particle spectra, that is, the matrix effect for carbonaceous chondrites is small, as long as neutron capture effects are not considered. The new model describes production rates for almost all cosmogenic radionuclides within the estimated uncertainties, which are in the range of 10%–15%. One exception is 53Mn in iron meteorites, for which the model significantly overestimates some of the experimental data. However, this might also be due to erroneous experimental data. Based on the new model calculations, 14C/10Be-, 36Cl/10Be-, and 41Ca/36Cl-production rate ratios, which are used to determine meteorite terrestrial ages, are systematically studied. The model predictions agree with experimentally found correlations. In addition, the 60Fe/53Mn production rate ratios, which are often used to distinguish interstellar from interplanetary 60Fe, are studied in some detail.