Precometary organic matter: A hidden reservoir of water inside the snow line

Abstract

The origin and evolution of solar system bodies, including water on the Earth, have been discussed based on the assumption that the relevant ingredients were simply silicates and ices. However, large amounts of organic matter have been found in cometary and interplanetary dust, which are recognized as remnants of interstellar/precometary grains. Precometary organic matter may therefore be a potential source of water; however, to date, there have been no experimental investigations into this possibility. Here, we experimentally demonstrate that abundant water and oil are formed via the heating of a precometary-organic-matter analog under conditions appropriate for the parent bodies of meteorites inside the snow line. This implies that H2O ice is not required as the sole source of water on planetary bodies inside the snow line. Further, we can explain the change in the oxidation state of the Earth from an initially reduced state to a final oxidized state. Our study also suggests that petroleum was present in the asteroids and is present in icy satellites and dwarf planets.

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

“…Assuming that primordial organic matter accumulated in the Semarkona parent body was similar to the organic mixture used in this study, at least 1.0-3.5 wt.% of organic matter have to initially present in the parent body necessary for producing the amount of water in Semarkona, since the water produced from the organic mixture was approximately 20 vol.% (Nakano et al 2020). Organic carbon in the bulk Semarkona meteorite as insoluble organic matter is 0.36 wt.% (Alexander et al 2007), thus if the water was delivered from organics, some of organic matter should have been lost through subsequent thermal processes.…”

“…Water, which is required for serpentinization, could be generated through organic reactions such as dehydration condensation of carboxylic acids and alcohols in the starting material at 300 °C (Hirakawa et al in revision). Nakano et al (2020) showed the formation of water from the same organic mixture we used in this study (Table S1). The amount of water formed depended on the content of hydroxy group (-OH) of the starting materials (Nakano et al 2020).…”

“…The olivine powder, the initial grain size of which was <200 µm, was ground before the experiments using an agate mortar to obtain a typical grain diameter of <50 µm. The organic mixture was prepared following the method of Kouchi et al (2002), Nakano et al (2002Nakano et al ( , 2003Nakano et al ( , 2020, and Hirakawa et al (in revision).…”

“…Their suggestion was that the D-rich water could originate from isotopically heterogeneous ice inherited from the interstellar ice (Piani et al 2015). In addition to these hypotheses, Nakano et al (2020) suggested that precometary organic matter formed in a molecular cloud could be another water source in ordinary chondrite parent bodies. High deuterium concentration in organic matter is well known in the interstellar medium (ISM) and the outer region of the Solar System (Owen et al 1986;Mauersberger et al 1988;Cecilia 2002;Parise et al 2004).…”

“…Chemical reactions of organic matter are frequently accompanied by simultaneous generation of by-products. Nakano et al (2020) performed heating experiments of organic mixtures up to 400 °C, which simulated the evolution of primordial organic matter in meteorite parent bodies, and they found various by-products including CO, CO 2 , and H 2 O during the experiments. These compounds in turn could have in uence on mineral alterations.…”