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
By: , and 

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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 (n(C)=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.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title 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
Series title Astrobiology
DOI 10.1089/ast.2011.0635
Volume 12
Issue 6
Year Published 2012
Language English
Publisher Mary Ann Liebert, Inc.
Description 13 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Astrobiology
First page 549
Last page 561