Did a Complex Carbon Cycle Operate in the Inner Solar System?

Abstract

Solids in the interstellar medium consist of an intimate mixture of silicate and carbonaceous grains. Because 99% of silicates in meteorites were reprocessed at high temperatures in the inner regions of the Solar Nebula, we propose that similar levels of heating of carbonaceous materials in the oxygen-rich Solar Nebula would have converted nearly all carbon in dust and grain coatings to CO. We discuss catalytic experiments on a variety of grain surfaces that not only produce gas phase species such as CH4, C2H6, C6H6, C6H5OH, or CH3CN, but also produce carbonaceous solids and fibers that would be much more readily incorporated into growing planetesimals. CH4 and other more volatile products of these surface-mediated reactions were likely transported outwards along with chondrule fragments and small Calcium Aluminum-rich Inclusions (CAIs) to enhance the organic content in the outer regions of the nebula where comets formed. Carbonaceous fibers formed on the surfaces of refractory oxides may have significantly improved the aggregation efficiency of chondrules and CAIs. Carbonaceous fibers incorporated into chondritic parent bodies might have served as the carbon source for the generation of more complex organic species during thermal or hydrous metamorphic processes on the evolving asteroid.

Nebula-Relay Hypothesis: The Chirality of Biological Molecules in Molecular Clouds

“…Complex organics in meteorites can also be generated in their parent asteroids through Fischer-Tropsch catalytic reactions (Cabedo et al, 2021). Nuth et al (2020) studied the complex carbon cycle on the evolving asteroid through thermal or hydrous metamorphic processes.…”

Molecular distribution and 13C isotope composition of volatile organic compounds in the Murchison and Sutter's Mill carbonaceous chondrites

“…In the outer protoplanetary disk, temperatures were low, and it is expected that the gas and icy dust grains present were rich in organic molecules and their precursors (Taquet et al., 2016; Tielens & Hagen, 1982). VOCs are thought to have formed in a variety of ways, including photochemistry, gas‐phase reactions, surface chemistry on dust and icy grains, and hydrothermal processes inside the parent asteroid (e.g., Charnley, 2001; Herbst & van Dishoeck, 2009; Hudson et al., 2008; Nuth et al., 2020; Vinogradoff et al., 2018). Recent analyses of carbonaceous chondrites and asteroid Ryugu materials, as well as experimental isotopic analysis using synthetic insoluble organic matter (IOM), suggest diverse locations such as the protosolar molecular cloud, the protoplanetary disk, and the asteroid parent bodies for the synthesis of soluble organics (Furukawa et al., 2021; Hopp et al., 2022).…”