Formation of Replicating Saponite from a Gel in the Presence of Oxalate: Implications for the Formation of Clay Minerals in Carbonaceous Chondrites and the Origin of Life
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Schumann-2012-Formation of Replicating Saponite from a Gel in the Presence of Oxalate.pdf
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Author(s)
Schumann, Dirk
Hartman, Hyman
Eberl, Dennis D.
Sears, S. Kelly
Hesse, Reinhard
Vali, Hojatollah
Date Issued
July 2012
Journal
Astrobiology
Publisher
Mary Ann Liebert
Citation
Schumann, Dirk et al. “Formation of Replicating Saponite from a Gel in the Presence of Oxalate: Implications for the Formation of Clay Minerals in Carbonaceous Chondrites and the Origin of Life.” Astrobiology 12.6 (2012): 549–561. Copyright©2011 Mary Ann Liebert, Inc. publishers.
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Final published version
Abstract
The potential role of clay minerals in the abiotic origin of life has been the subject of ongoing debate for the past several decades. At issue are the clay minerals found in a class of meteorites known as carbonaceous chondrites. These clay minerals are the product of aqueous alteration of anhydrous mineral phases, such as olivine and orthopyroxene, that are often present in the chondrules. Moreover, there is a strong correlation in the occurrence of clay minerals and the presence of polar organic molecules. It has been shown in laboratory experiments at low temperature and ambient pressure that polar organic molecules, such as the oxalate found in meteorites, can catalyze the crystallization of clay minerals. In this study, we show that oxalate is a robust catalyst in the crystallization of saponite, an Al- and Mg-rich, trioctahedral 2:1 layer silicate, from a silicate gel at 60°C and ambient pressure. High-resolution transmission electron microscopy analysis of the saponite treated with octadecylammonium (nC=18) cations revealed the presence of 2:1 layer structures that have variable interlayer charge. The crystallization of these differently charged 2:1 layer silicates most likely occurred independently. The fact that 2:1 layer silicates with variable charge formed in the same gel has implications for our understanding of the origin of life, as these 2:1 clay minerals most likely replicate by a mechanism of template-catalyzed polymerization and transmit the charge distribution from layer to layer. If polar organic molecules like oxalate can catalyze the formation of clay-mineral crystals, which in turn promote clay microenvironments and provide abundant adsorption sites for other organic molecules present in solution, the interaction among these adsorbed molecules could lead to the polymerization of more complex organic molecules like RNA from nucleotides on early Earth. Key Words: Saponite—2:1 layer silicates—Origin of life—Silicate-organics interactions—Oxalate as a catalyst—Crystallization of saponite from silica gel. Astrobiology 12, 549–561.
MIT Department
Massachusetts Institute of Technology. Center for Biomedical Engineering
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1089/ast.2011.0635
