¹Chunlai Li et al. (>10)
Nature 569, 378-382 Link to Article [https://doi.org/10.1038/s41586-019-1189-0]
¹Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China

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^1,2,3Anhuai Lu et al. (>10)
Proceedings of the National Academy of Sciences of the United States of America 116, 9741-9746 Link to Article [https://doi.org/10.1073/pnas.1902473116]
¹Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, 100871 Beijing, People’s Republic of China
²The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, 100871 Beijing, People’s Republic of China
³The Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, School of Geosciences and Info-Physics, Central South University, 410083 Changsha, People’s Republic of China

Sunlight drives photosynthesis and associated biological processes, and also influences inorganic processes that shape Earth’s climate and geochemistry. Bacterial solar-to-chemical energy conversion on this planet evolved to use an intricate intracellular process of phototrophy. However, a natural nonbiological counterpart to phototrophy has yet to be recognized. In this work, we reveal the inherent “phototrophic-like” behavior of vast expanses of natural rock/soil surfaces from deserts, red soils, and karst environments, all of which can drive photon-to-electron conversions. Using scanning electron microscopy, transmission electron microscopy, micro-Raman spectroscopy, and X-ray absorption spectroscopy, Fe and Mn (oxyhydr)oxide-rich coatings were found in rock varnishes, as were Fe (oxyhydr)oxides on red soil surfaces and minute amounts of Mn oxides on karst rock surfaces. By directly fabricating a photoelectric detection device on the thin section of a rock varnish sample, we have recorded an in situ photocurrent micromapping of the coatings, which behave as highly sensitive and stable photoelectric systems. Additional measurements of red soil and powder separated from the outermost surface of karst rocks yielded photocurrents that are also sensitive to irradiation. The prominent solar-responsive capability of the phototrophic-like rocks/soils is ascribed to the semiconducting Fe- and Mn (oxyhydr)oxide-mineral coatings. The native semiconducting Fe/Mn-rich coatings may play a role similar, in part, to photosynthetic systems and thus provide a distinctive driving force for redox (bio)geochemistry on Earth’s surfaces.

^1,2Junyue Tang,¹ Shengyuan Jiang,¹Qiquan Quan,¹Jieneng Liang,¹Yi Shen,¹Ye Tian,³Fengpei Yuan
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2019.05.005]
¹State Key Laboratory of Robotics and System, Harbin Institute of Technology, No.92, Xidazhi St., Nangang Dist, Harbin, 150001, PR China
²Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Rd., Evanston, IL, 60208, USA
³Department of Mechanical, Aerospace and Biomedical Engineering, The University of Tennessee, Knoxville, 124 Perkins Hall, Knoxville, TN, 37996, USA

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¹Didier Gourier et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.05.009]
¹Chimie ParisTech, PSL University, CNRS, Institut de Recherche de Chimie de Paris (IRCP), F-75005 Paris, France
Copyright Elsevier

Electron paramagnetic resonance (EPR) analysis of carbonaceous, volcanic, tidal sediments from the 3.33 Ga-old Josefsdal Chert (Kromberg Formation, Barberton Greenstone Belt), documents the presence of two types of insoluble organic matter (IOM): (1) IOM similar to that previously found in Archean cherts from numerous other sedimentary rocks in the world and of purported biogenic origin; (2) anomalous IOM localized in a 2 mm-thick sedimentary horizon. Detailed analysis by continuous-wave-EPR and pulse-EPR reveals that IOM in this layer is similar to the insoluble component of the hydrogenated organic matter in carbonaceous chondrites, suggesting that this narrow sedimentary horizon has preserved organic matter of extraterrestrial origin. This conclusion is supported by the presence in this thin layer of another anomalous EPR signal at g = 3 attributed to Ni-Cr-Al ferrite spinel nanoparticles, which are known to form during atmospheric entry of cosmic objects. From this EPR analysis, it was deduced that the anomalous sedimentary layer originates from deposition, in a nearshore environment, of a cloud of tiny dust particles originating from a flux of micrometeorites falling through the oxygen-poor Archean atmosphere.