Thorsten Kleine^1,2, Theodor Steller², Christoph Burkhardt^1,2, Francis Nimmo³
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115519]
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
³Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
Copyright Elsevier

The origin of volatile elements in Mars and whether these elements derive from the inner or outer solar system is unclear. Here we show that Mars exhibits nucleosynthetic zinc (Zn) isotope anomalies similar to those of non‑carbonaceous (NC) but distinct from carbonaceous (CC) meteorites. Like for non-volatile elements, Mars’ Zn isotope composition is intermediate between those of enstatite and ordinary chondrites, demonstrating that Mars acquired volatile elements predominantly from its inner solar system building blocks. The Zn isotope data limit the contribution of CI chondrite-like material to Mars to 4% by mass at most and show that Mars accreted less CC material than Earth. The origin of these disparate CC fractions is unclear, but can place constraints on how and when CC-type material was delivered to the inner solar system.

Zixu Zhao, Jian Chen, Zongcheng Ling, Xuejin Lu, Zexi Li
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115531]
Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, School of Space Science and Physics, Shandong University, Weihai 264209, China
Copyright Elsevier

The timeline of volcanic activity is critical for constraining the thermal evolution of the Moon. The spatial extents of mare basalts, major products of lunar volcanism, have been precisely extracted from LROC (Lunar Reconnaissance Orbiter Camera) image mosaics. With the maria extents newly extracted from LROC mosaics, we found that a large area of mare basalts in the junction of Oceanus Procellarum, Mare Imbrium, Mare Insularum, and Mare Vaporum (the PIV region) has not yet been dated. This study analysed the chronology, composition, and mineralogy of the PIV region, aiming to finish the picture of basaltic volcanism in the Procellarum region, which is a key puzzle of our global geological mapping of the Moon. According to the topographical, spectral, and compositional characteristics, mare units of the PIV region are defined, and the crater size frequency distribution is measured. The primary craters with diameters >0.1 km in the PIV region are measured, and the absolute model ages of basalt units between ~3.78 Ga and ~ 1.71 Ga are derived. Most western PIV basalt units are Eratosthenian-aged, while eastern units mostly formed in the Imbrian period. The spectra of 4965 small impact craters are extracted to interpret the mineral compositions of the PIV basalt units using Chandrayaan-1 Moon Mineralogy Mapper data. Using a Modified Gaussian Model, the reflectance spectra are deconvoluted, and the obtained modal proportions of mafic minerals show low olivine and high low-Ca pyroxene abundances in the eastern PIV region, while the western region features high olivine and calcic pyroxene concentrations. Three episodes of volcanic events occurring in the PIV region are identified. The first (main) occurred at approximately 3.5 Ga (Late Imbrian), with erupted lava flows with less evolved compositions covering most of the PIV area. The peak of volcanic activity in the Eratosthenian period occurred around 2.5 Ga, where mare basalts with moderately evolved compositions and mineralogy were formed. The last major eruption occurred at approximately 1.8 Ga, forming mare basalts with highly evolved compositions.