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The origin and emergence of life under impact bombardment - PubMed

  • ️Sun Jan 01 2006

The origin and emergence of life under impact bombardment

Charles S Cockell. Philos Trans R Soc Lond B Biol Sci. 2006.

Abstract

Craters formed by asteroids and comets offer a number of possibilities as sites for prebiotic chemistry, and they invite a literal application of Darwin's 'warm little pond'. Some of these attributes, such as prolonged circulation of heated water, are found in deep-ocean hydrothermal vent systems, previously proposed as sites for prebiotic chemistry. However, impact craters host important characteristics in a single location, which include the formation of diverse metal sulphides, clays and zeolites as secondary hydrothermal minerals (which can act as templates or catalysts for prebiotic syntheses), fracturing of rock during impact (creating a large surface area for reactions), the delivery of iron in the case of the impact of iron-containing meteorites (which might itself act as a substrate for prebiotic reactions), diverse impact energies resulting in different rates of hydrothermal cooling and thus organic syntheses, and the indiscriminate nature of impacts into every available lithology-generating large numbers of 'experiments' in the origin of life. Following the evolution of life, craters provide cryptoendolithic and chasmoendolithic habitats, particularly in non-sedimentary lithologies, where limited pore space would otherwise restrict colonization. In impact melt sheets, shattered, mixed rocks ultimately provided diverse geochemical gradients, which in present-day craters support the growth of microbial communities.

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Figures

Figure 1
Figure 1

Darwin's warm little pond—the impact crater as a prebiotic reactor. Some of the diversity of characteristics of impact structures that make them favourable sites for prebiotic reactions are shown.

Figure 2
Figure 2

Impact craters as a habitat. Some of the characteristics of impact craters that make them favourable sites for micro-organisms are shown.

Figure 3
Figure 3

Organisms associated with impact melt sheets (suevites) in the Haughton impact structure, Canada. (a) A biofilm of organisms associated with a cavity inside the material (scale bar 0.1 mm); (b) microfungi associated with the biofilms (scale bar 30 μm); (c) the diverse mineralogy of the breccia (granites, dolomite, gneiss, sandstones) provides a geochemically diverse environment for microorganisms (scale bar 0.3 mm)

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