Bulk chemical characteristics of soluble polar organic molecules formed through condensation of formaldehyde: Comparison with soluble organic molecules in Murchison meteorite

Yuki Isono, Shogo Tachibana, Hiroshi Naraoka, François Régis Orthous-Daunay, Laurette Piani, Yoko Kebukawa

Research output: Contribution to journalArticle

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Abstract

Carbonaceous chondrites contain up to 2 wt% organic carbon, which is present as acid and solvent insoluble solid organic matter (IOM) and solvent soluble organic matter (SOM). The extraterrestrial organic matter should record chemical processes occurred in different environments in the early history of the Solar System, and the role of parent body aqueous alteration in the synthesis or subsequent modification of IOM and SOM still requires accurate constraints. We conducted hydrothermal experiments to simulate the synthesis of organic molecules during aqueous alteration on small bodies. Bulk chemical characteristics of soluble organic matter synthesized from formaldehyde in aqueous solutions were studied to compare them with that of chondritic SOM. We found that the redox state of synthesized organic molecules depends on temperature; the molecules become richer in hydrogen at higher temperatures. This can be explained by a cross-disproportionation reaction between organic molecules and formic acid, which occurs as a side reaction of the aldol condensation and works more effectively at higher temperatures. Comparison of the bulk chemical characteristics between the synthesized molecules and SOM extracted from the Murchison meteorite with methanol shows that the soluble organic molecules in Murchison are more reduced than the synthesized molecules. Considering the temperature condition for aqueous alteration on the CM parent body that is lower than or equivalent to the experimental temperatures, the reduced nature of Murchison organic molecules requires a reducing environment for them to be formed during hydrothermal alteration or imply that processes other than hydrothermal alteration were responsible for their synthesis. In case of hydrothermal synthesis, reducing conditions might be established by the interaction between water and iron-bearing silicates or metals on the parent body.

Original languageEnglish
Pages (from-to)41-51
Number of pages11
JournalGEOCHEMICAL JOURNAL
Volume53
Issue number1
DOIs
Publication statusPublished - Jan 1 2019

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Murchison meteorite
Meteorites
formaldehyde
Biological materials
Formaldehyde
condensation
Condensation
organic matter
Molecules
molecules
parent body
organic solids
formic acid
synthesis
hydrothermal alteration
Bearings (structural)
Temperature
Silicates
carbonaceous chondrites
acids

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

Bulk chemical characteristics of soluble polar organic molecules formed through condensation of formaldehyde : Comparison with soluble organic molecules in Murchison meteorite. / Isono, Yuki; Tachibana, Shogo; Naraoka, Hiroshi; Orthous-Daunay, François Régis; Piani, Laurette; Kebukawa, Yoko.

In: GEOCHEMICAL JOURNAL, Vol. 53, No. 1, 01.01.2019, p. 41-51.

Research output: Contribution to journalArticle

Isono, Yuki ; Tachibana, Shogo ; Naraoka, Hiroshi ; Orthous-Daunay, François Régis ; Piani, Laurette ; Kebukawa, Yoko. / Bulk chemical characteristics of soluble polar organic molecules formed through condensation of formaldehyde : Comparison with soluble organic molecules in Murchison meteorite. In: GEOCHEMICAL JOURNAL. 2019 ; Vol. 53, No. 1. pp. 41-51.
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