^1,2,3Sheng Gou et al. (>10)
Earth and Planetary Science Letters 648, 119091 Link to Article [https://doi.org/10.1016/j.epsl.2024.119091]
¹Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100101, China
³State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, 999078, China
Copyright Elsevier

China’s Chang’e-6 (CE6) sample return mission targeted the southern part of the Apollo basin inside the South Pole-Aitken (SPA) basin on the lunar farside. The spectrally peculiar mare basalts in the CE6 landing area had undergone complex evolution: (1) At least three mare floodings with low- to intermediate-titanium (Ti) contents and a total volume of > 798 km3 occurred during the Imbrian and Eratosthenian periods; (2) The scales of basalt eruption decreased with time, and nine wrinkle ridges (WRs) formed during different stages of floodings; (3) Exotic non-mare materials at the CE6 sampling site might be chiefly from noritic Chaffee S crater (∼16.6 cm-thick) and anorthositic Vavilov crater (∼1.7 cm-thick). (4) Impact gardening would mix local low/intermediate-Ti basalts and exotic non-mare materials. After analyzing the local basalt-dominant samples collected by the CE6 probe with sophisticated instruments in the terrestrial laboratories, a series of lunar scientific problems would be addressed definitely, for example, the ages and compositions of the mare basalts, the evolution of the low- and intermediate-Ti basalts, and the effects of solar wind on the lunar regolith. In addition, if the returned samples contain exotic impact melts and ejecta of both the Apollo and SPA basins, analyses on these non-mare materials would help to constrain the timing of the Apollo and SPA impact events, the extent and composition of the proposed (differentiated) SPA melt pool, and even the compositions of the lunar lower crust/upper mantle. Addressing these fundamental problems would be a significant contribution to the lunar science community.

¹Nadja Drabon,¹Andrew H. Knoll,²Donald R. Lowe,³Stefano M. Bernasconi, ¹Alec R. Brenner,²David A. Mucciarone
Proceedings of the National Academy of Science of the United States of America (PNAS) 121, e2408721121 Open Access Link to Article [https://doi.org/10.1073/pnas.2408721121]
¹Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138
²Department of Earth and Planetary Sciences, Stanford University, Stanford, CA 94305
³Department of Earth Sciences, ETH Zürich, Zürich 8092, Switzerland

Large meteorite impacts must have strongly affected the habitability of the early Earth. Rocks of the Archean Eon record at least 16 major impact events, involving bolides larger than 10 km in diameter. These impacts probably had severe, albeit temporary, consequences for surface environments. However, their effect on early life is not well understood. Here, we analyze the sedimentology, petrography, and carbon isotope geochemistry of sedimentary rocks across the S2 impact event (37 to 58 km carbonaceous chondrite) forming part of the 3.26 Ga Fig Tree Group, South Africa, to evaluate its environmental effects and biological consequences. The impact initiated 1) a giant tsunami that mixed Fe2+-rich deep waters into the Fe2+-poor shallow waters and washed debris into coastal areas, 2) heating that caused partial evaporation of surface ocean waters and likely a short-term increase in weathering and erosion on land, and 3) injection of P from vaporization of the S2 bolide. Strata immediately above the S2 impact event contain abundant siderites, which are associated with organic matter and exhibit light and variable δ13Ccarb values. This is consistent with microbial iron cycling in the wake of the impact event. Thus, the S2 impact likely had regional, if not global, positive and negative effects on life. The tsunami, atmospheric heating, and darkness would likely have decimated phototrophic microbes in the shallow water column. However, the biosphere likely recovered rapidly, and, in the medium term, the increase in nutrients and iron likely facilitated microbial blooms, especially of iron-cycling microbes.