Aqueous alteration without initial water: possibility of organic-induced hydration of anhydrous silicates in meteorite parent bodies

Abstract

Early evolution of Solar System small bodies proceeded through interactions of mineral and water. Melting of water ice accreted with mineral particles to the parent body results in the formation of secondary minerals, the so-called aqueous alteration. Formation of phyllosilicates from anhydrous silicates is a typical alteration effect recorded in primitive meteorites. In addition to mineral and water, organic matter could have been also a significant component in meteorite parent bodies. However, the role of organic matter in the alteration of silicates is not well understood. We conducted a heating experiment of anhydrous silicate (olivine) with a mixture of organic compounds which simulated primordial organic matter in the Solar System. Dissolution and precipitation features were confirmed on the olivine surface after heating at 300 °C for 10 days, and proto-phyllosilicates were formed in the precipitation area. Magnesite was also detected as concomitant mineral phase. These minerals could be the evidence of aqueous alteration and carbonation of olivine induced by water generated through decomposition of the organic compounds with hydroxy groups. Our result showed that the in situ formation of hydrated silicates through a mineral–organic interaction without the initial presence of water. It further implies that formation of phyllosilicates on the olivine surface in contact with organic matter can occur in meteorite parent bodies which formed inside the H2O snow line but accreted with organic matter, initially without water. Water formed through decomposition of organic matter could be one candidate for hydrous silicate formation, for example, in ordinary chondrites from S-type asteroids inside the H2O snow line. Although the origin of water in ordinary chondrites is under debate, water generation from organic matter may also explain the D-rich water in ordinary chondrites because primordial organic matter is known to be D rich.

Polyaromatic Units Set the Albedo of Dark Extraterrestrial Materials

“…This dependence may indicate a possible role played by the phyllosilicates in the protection and/or formation of organic matter in hydrated IDPs. It could also indicate the role of organic matter on phyllosilicate formation as reported by Hirakawa et al (2021). This process occurs on dry meteorites such as meteorites of the CO and CV groups and is therefore associated with significant graphitization of organic matter (e.g., Nakamura 2005;Hirakawa et al 2021).…”

“…The hydration process on CM-type meteorites comes from the melting of the ice contained in the parent body by the heating induced by radioactive decay of the elements with short periods (e.g., Brearley 2006;Merk & Prialnik 2006 and references therein). Liquid water circulation on parent bodies causes the alteration of minerals (hydration) and leads to redistribution and migration of elements (Brearley 2006;King et al 2017;Hirakawa et al 2021). Yesiltas & Kebukawa (2016) also showed a correlation between organic matter and phyllosilicates in grains of the Tagish Lake meteorite (based on the OH band at 3050 cm −1 ) and concluded that phyllosilicates can play a role in the formation and/or protection of organic matter in the parent body.…”

Are Clay Minerals Systematically the Products of Aqueous Alteration in Cosmic Bodies?

“…They demonstrate that when evidence of alteration exists, it is predominantly isochemical at the scale of the chondrules and matrix, likely confined to zones within 100-200 µm around anhydrous chondrules. Moreover, Hirakawa et al [52] proved that organic mat- A schematic illustration of the three modes of water rock interaction in asteroid (modified after [49]). The diagram illustrates porosity at a macroscopic scale (in kilometers), while the calculations are conducted using microscopic (grain-scale) porosity for accuracy [49].…”

“…They demonstrate that when evidence of alteration exists, it is predominantly isochemical at the scale of the chondrules and matrix, likely confined to zones within 100-200 µm around anhydrous chondrules. Moreover, Hirakawa et al [52] proved that organic matter-mineral interaction could also lead to in-situ aqueous alteration through water generation by decomposition of organic compounds with hydroxy groups after heating. In this case, it forms locally hydrated phyllosilicates on the surface of olivine in carbonaceous chondrites.…”

Chirality in Organic and Mineral Systems: A Review of Reactivity and Alteration Processes Relevant to Prebiotic Chemistry and Life Detection Missions

“…At similar temperatures, but in an open system where fluids are flowing through the rock and altering the composition, is referred to as metasomatism [336]. Some recent experimental studies have suggested that the initial parent body composition need not contain water, as heat from impact [337] or organic degradation [338] could induce aqueous alteration on parent bodies.…”