¹A.Karthi,¹S.Arivazhagan
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114844]
¹Centre for Applied Geology, The Gandhigram Rural Institute – Deemed to be University, Gandhigram, Dindigul, Tamilnadu, India
Copyright Elsevier

The lunar multiring mare basins have different ages, compositions and are associated with the diverse unit of mare deposits, providing evidence for the origin and evolution of the lunar crust. The multiring basins offer the opportunity to assess many unknown questions that may reveal the lunar geologic standpoint. The Mare Orientale basin is one of the youngest impact multiring basins on the Moon, which covers about 930 km in diameter and coordinates centered at 20⁰S 95⁰W. In the present study, the compositional, topographical, and chronological studies have been done by using Moon Mineralogy Mapper (M³) from Chandrayaan-1 orbiter and Lunar Reconnaissance Orbiter Camera-Wide Angle Camera (LROC-WAC) image from Lunar Reconnaissance Orbiter (LRO). The M³ data used to map the Optical maturity (OMAT), FeO & TiO₂ concentrations of the basin. The Standard Band Ratio (SBR) of the Orientale basin has been prepared to discriminate the different mare and highland lithologies. The 1 μm and 2 μm band depths have been mapped to demarcate the mafic minerals such as olivine and pyroxenes. The age of the Orientale basin mare units was mapped as Orientale event (3.72 Ga – Upper Imbrian), Orientale South West (3.7 Ga), Orientale West unit (3.37 Ga), Lacus Veris North unit- 1, 2, and 3 (3.1 Ga, 2.63 Ga, and 3.3 Ga), Lacus Veris East (2.9 Ga), Lacus Autumni – North (3.1 Ga), Middle (2.01 Ga), South (2.27 Ga) and Kopff crater (mare) (2.92 Ga) by using LROC-WAC data through Crater Size Frequency Distribution (CSFD) technique. Characterization of M³ reflectance spectra profiles was done to map the Orientale basin lithologies like olivine, pyroxene (low calcic and high calcic), plagioclase, ilmenite, Mg-spinel, and olivine – pyroxene mixtures that are present in the anorthositic, basaltic, noritic, and gabbroic rocks. It is revealed that the Orientale basin could have been formed either by global thermal evolution and basin mare volcanic evolution or pressure release melting and associated with secondary convection.

^1,2,3R.Martinez,¹A.Agnihotri,³E.F.da Silveira,⁴M.E.Palumbo,⁴G.Strazzulla,¹P.Boduch,¹A.Domaracka,¹H.Rothard
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114830]
¹Centre de Recherche sur les Ions, les Matériaux et la Photonique, Normandie University, ENSICAEN, UNICAEN, CEA, CNRS, CIMAP, 14000 Caen, France
²Physics Department, Universidade Federal do Amapá, Brazil
³Physics Department, Pontifícia Universidade Católica do Rio de Janeiro, Rua Marquês de São Vicente 225, 22453-900 Rio de Janeiro, RJ, Brazil
⁴INAF-Osservatorio Astrofisico di Catania, Italy
Copyright Elsevier

Silicates are ubiquitous in space. They dominate the surfaces of the inner rocky planets (Mercury in the case of the Solar System), the Moon, and asteroids, forming the major part of the non-volatile material. The physical and chemical properties of the rocky surfaces are determined not only by their initial composition but also by the processes occurring on them. Here we discuss one of these processes; irradiation by energetic cosmic particles that induces many effects among which structural changes and sputtering, the latter contributing to the formation of exospheres. In the current work we report the results of experiments conducted on anorthite, jadeite and nepheline silicates that have been irradiated with energetic heavy ions with the aim to better understand the interaction of galactic cosmic rays, solar wind, and solar energetic particles with planetary and small body surfaces. The sputtering effects induced by energetic (MeV/u) multicharged heavy ions (e.g., ¹⁰⁵Rh and ¹⁴⁰Ba) were analyzed by the PDMS-TOF-SIMS technique (plasma desorption mass spectrometry – time-of-flight secondary ion mass spectrometry). Positive and negative secondary ionic species are identified: Na⁺, K⁺, Al⁺, Ca⁺, SiO₂⁻. Ejection of (SiO₂)_n⁻ and (AlSi)O_m⁻ cluster series are also observed. Less frequent, negative ion yields are one order of magnitude less than positive ones, or greater, which is the case for nepheline, with 0.671 ions impact⁻¹ for positive and 0.126 ions impact⁻¹ for negative ions. The results concerning ejection of ionic species show, for instance, that the Na⁺/K⁺ ratio is ~2.5, which is in very good agreement with that observed in the Hermean exosphere found to be ~2.3.