¹Fabrizio Di Fiore, ²Michele Cassetta
Journal of Geophysical Research: Planets, 131, e2026JE009904 Open Source Link to Article [DOI: 10.1029/2026JE009904]
¹Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy
²Department of Engineering for Innovation Medicine, University of Verona, Verona, Italy
Published by arrangement with John Wiley & Sons

Silicate melt viscosity plays a pivotal role in the evolution of rocky bodies within the Solar System, exerting first-order control on mantle differentiation and stratification, while dictating the metal-silicate separation and the subsequent volcanic activity. Thus, predicting the viscosity of planetary compositions is essential to model and better understand their thermomechanical evolution. Notably, the chemical signatures of primordial planetary magmas, marked by extreme Fe, Mg, and Ca enrichment, drive a highly depolymerized and fragile rheological regimes that frequently fall beyond the calibration data sets used to model the viscosity. In this study, we characterize the effect on viscosity by doping a basalt with iron, magnesium, and calcium to resemble an exotic planetary composition. By integrating high- and low-temperature viscometry with Raman spectroscopy and ultrasonic data, we show that this chemical enrichment significantly impacts the rheology, elasticity and the structural organization of the doped melt. In particular, viscosity decreases ∼2 times at high temperatures compared to the original basalt. This behavior is driven by the extreme depolymerization of the melt, and it is reflected in a shift toward Q² and Q¹ structural units. Vibrational analysis via the Boson Peak confirms a highly fragile state characterized by noticeably small correlation lengths. We tested several widely used semi-empirical models and found that while traditional empirical formulations struggle to accurately predict the viscosity of these exotic compositions, spectroscopy-based frameworks provide significantly better accuracy. This performance highlights the fundamental link between atomic-scale vibrational properties and melt-scale dynamics.

¹S. R. Baker, ^1,2,3,4B. L. Ehlmann
Journal of Geophysical Research: Planets, 131, e2025JE009605 Open Source Link to Article [DOI: 10.1029/2025JE009605]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
²Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA
³Department of Geological Sciences, University of Colorado, Boulder, CO, USA
⁴Department of Astrophysical & Planetary Sciences, University of Colorado, Boulder, CO, USA
Published by arrangement with John Wiley & Sons

Aluminum phyllosilicates occur in 1–10s of km² exposures of Noachian (∼3.7 Ga) rock across Mars and typically appear stratigraphically above Fe/Mg-phyllosilicates. These units have been proposed to represent pedogenic basalt weathering sequences. We examine Al-phyllosilicates in the Nili Fossae region, combining mineral maps generated from imaging spectroscopy with digital elevation models and high-resolution imagery to determine mineral assemblages, their geologic relationships, and their history of formation. We find that the Al-phyllosilicate is dominantly kaolinite and lacks associated Fe oxide. The Al-phyllosilicates typically have a distinct texture relative to Fe/Mg-phyllosilicate units, indicating an unconformity, and two different protoliths rather than formation as a pedogenic weathering sequence. Layers in some kaolinite deposits and their preferential association with sedimentary basins suggest reworked sedimentary material. The most plausible source is an Al/Si-enriched (non-basaltic) airfall volcanic deposit. We detect sparse jarosite closely associated with kaolinite but not Fe/Mg-phyllosilicate. We interpret that the jarosite, which is metastable under present surface conditions, formed from reaction between Fe-enriched fluids and S that is found sufficiently only within the kaolinite-bearing protolith. Collectively, these observations suggest less intense near-surface oxidative weathering than the basalt pedogenesis hypothesis, namely, an upper bound of several million cumulative years of aqueous activity in Nili Fossae that largely ended after the formation of jarosite. Detection of Al-phyllosilicate-bearing float rocks in nearby Jezero Crater by the Perseverance Rover shows that sample return has potential to conclusively determine processes and environmental conditions forming Nili Fossae’s distinctive Al-phyllosilicates.

¹Marco A. G. Andreoli (>10)
Journal of Geophysical Research: Planets, 131, e2026JE009901 Link to Article [DOI: 10.1029/2026JE009901]
¹School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
Published by arrangement with John Wiley & Sons

In this paper we report the discovery, in the Gilf Kebir Plateau of southwest Egypt, of the first natural occurrence of Diamond-Like-Carbon, of microdiamonds, and new ultra-high T (≥1300°C) silicates, phosphates in boulders and pebbles of a mullite and magnetite melt rock. We also report, in the regolith of the Libyan Desert Glass (LDG) strewn field, comparable mullite-magnetite pebbles and, in paleosols, Diamond-Like-Carbon, N-rich amorphous carbon, aliphatic hydrocarbons, moissanite, and metallic spherules and grains of native Ti. These findings point to a ∼350 km, south to north strewnfield of melt rocks and their related disaggregated debris formed by the impact of a carbonaceous meteorite in the Jebel Uweinat, near the Egypt-Sudan border. At the northern end of their fluvial depository, the reworked debris co-mingled with the LDG strewnfield, likely originated from a second impact in the Gilf Kebir. The date of the diamonds-forming mullite impact melt is undetermined but tentatively linked to the 29 Ma event of the LDG, because disordered carbon + aliphatic compounds were found in a glass and in the, extraterrestrial (extrasolar) “Hypatia” from the same areas. The latter is considered as relic of the original, parent impactor.