Formation of Crystalline Silica–Carbonate Biomorphs of Alkaline Earth Metals (Ca, Ba, Sr) from Ambient to Low Temperatures: Chemical Implications during the Primitive Earth’s Life

Abstract

The Earth has undergone at least four great glaciations, during which the ice layers and the glaciers have expanded all over the planet, corresponding to significant drops in global temperatures that lasted millions of years. Since the Precambrian era, ice ages have occurred at intervals of several millions of years. It is considered that the impact on the biosphere was large, because life was on the brink of disappearing completely from the planet. During these glaciation periods, carbon was reassigned, with the subsequent formation of carbonates called cap carbonates, which present stromatolite-like activity. These findings prove that life was conserved even during the glacial period. Knowledge on life conservation during the glacial period through stromatolites that have endured until the present day, is of special relevance. In recent investigations, in vitro structures have been synthesized; these crystalline aggregates have been named biomorphs because they mirror the morphologies of primitive organisms called Precambrian cherts. These biomorphs have been synthesized at different temperatures (from room temperature to lower ones). The aim of the present work was to synthesize CaCO 3 , BaCO 3 , and SrCO 3 silica−carbonate biomorphs at three low temperatures (4 °C, −20 °C, and −70 °C). CaCO 3 biomorphs present almost the same morphology at all temperatures with a calcite crystalline structure, whereas BaCO 3 and SrCO 3 biomorphs present remarkably different morphologies depending on temperature with witherite and strontianite crystalline structure, respectively.

Silica-Carbonate of Ba(II) and Fe2+/Fe3+ Complex as Study Models to Understand Prebiotic Chemistry

“…As seen in Figure 1 , the control silica-carbonates obtained in standard conditions of temperature, pressure, and CO 2 (STP) depict a morphology of leaves and helices on both glass and silicon wafers ( Figure 1 A), which correspond to characteristic morphologies of the biomorphs previously reported. 19 − 26 …”

Influence of Abiotic Factors in the Chemical Origin of Life: Biomorphs as a Study Model

“…In contrast, the BaCO 3 and SrCO 3 biomorphs showed a different morphology depending on the temperature ( Figure 3 ). 20 …”

“…Low: (b) 4 °C, (c) −20 °C, and (d) −70 °C. Adapted in part from ref ( 20 ). Copyright 2020 American Chemical Society.…”

“… 5 The different morphologies of the biomorphs obtained in a temperature range from −70 to 70 °C allow one to consider the large variety of morphologies adopted by the first organisms in the Precambrian era. 20 Some of these morphologies were lost, others were modified, and only some were conserved along time and by the consequent modification of atmospheric conditions. These data allow inferring a correlation, but there are innumerable questions to be resolved about the origin of life, which will only be achieved with the joint effort of diverse groups and knowledge areas.…”

Ariel – a window to the origin of life on early earth?

“…These supramolecular structures show inorganic membranes with a different internal and external composition. The membrane interior is mainly composed from metal silicates, while ordered aggregates of silica largely prevail outside [206]. The chemo-physical asymmetry of the whole system has relevant consequences for prebiotic chemistry since it generates pH and electrochemical gradients able to act as a driving-force for the synthesis of biomolecules [207].…”