biosphere Archives

Two proposed mechanisms for H2O2 generation at quartz–water interfaces. (A) Stress-induced cleavage of Si–O bonds. Applied force is represented by a linear falling potential (dashed line), which is added to the Morse potential of the unstretched Si–O bond (dotted line), thus resulting in a force-deformed Morse potential (solid line). The new dissociation energy D′ is smaller than D in the case of a stretching force. Modified after Kauzmann et al. (42). The probability of generation of surface-bound radicals in quartz therefore increases during mechanical processes. (B) Contact of water on freshly fractured surface of abraded quartz. Modified after Schoonen et al. (32). (C) Generation of H2O2 and O2 in the reaction between H2O and oxygen radical (≡SiO•). (D) Generation of rocky H2O2 and O2 in the reaction between H2O and peroxy radical (≡SiOO•). Surface-bound radicals are formed through homolysis of Si–O bonds, including ≡SiO•, ≡SiOO•, and E′ center (≡Si•), while surface charges (≡Si+ and ≡SiO–) for heterolysis. Silanol groups (≡SiOH) are end products on quartz surface after hydroxylation. -- Guangzhou Institute

Astrogeology, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Habitable Zones, Origin & Evolution of Life, Press Release

A Novel Origin Of Abiotic Oxidants On Early Earth: Minerals

by Keith CowingMarch 23, 2023March 23, 2023

Molecular oxygen (O2) is essential for respiration on today’s Earth, but the early atmosphere was almost devoid of oxygen until the Great Oxidation Event. How then did Earth’s atmosphere become […]

Astrochemistry, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Press Release

Detecting Biospheres from Thermodynamic Disequilibrium in Planetary Atmospheres

by Keith CowingMarch 30, 2015

Atmospheric chemical disequilibrium has been proposed as a method for detecting extraterrestrial biospheres from exoplanet observations. Chemical disequilibrium is potentially a generalized biosignature since it makes no assumptions about particular […]