Ancient Earth

Becker RH, Clayton RN (1976) Oxygen isotope study of a Precambrian banded iron-formation. Hamersley Range, Western Australia. Geochim Cosmochim Acta 40 1153-1165 Beard BL, Johnson CM (2004) Fe isotope variations in the modem and ancient earth and other planetary bodies. Rev Mineral Geochem 55 319-357... 

Beard BL, Johnson CM (2004) Ee isotope variations in the modem and ancient earth and other planetary bodies. Rev Mineral Geochem 55 319-357... 

Fe Isotope Variations in the Modern and Ancient Earth and Other Planetary Bodies... 

The rate of the biotic reduction of Fe oxides by a strain of Corynehacterium under 02-free conditions followed the order natural ferrihydrite > synthetic goethite > hematite (Fischer (1988) (Fig. 12.29) in accordance with the sequence in reducibility by Fe-reducing bacteria isolated from a eutrophic lake sediment (Jones et al., 1983). Iron from ferrihydrite reduced by Shewandla alga was found to be isotopically lighter than that of the ferrihydrite Fe by a 5 ( Fe/ " Fe) of 1.3 %o This difference may be used to trace the distribution of microorganisms in modern and ancient earth (Beard etal. 1999). 

The experiment that Stanley Miller reported in 1952 stunned the world. As Miller has readily explained, however, that experiment was not the first such one he tried. Earlier he had set up his apparatus in a somewhat different manner and found that some oil was formed, but no amino acids. Since he thought amino acids would be the most interesting chemicals to find, he jiggled the apparatus around in hopes of producing them. Of course, if conditions on the ancient earth actually resembled Miller s unsuccessful attempts, then in reality no amino acids would have been produced. 

Sleep N. H. and Zahnle K. (2001) Carbon dioxide cycling and impheations for chmate on ancient Earth. ]. Geophys. Res. 106, 1373-1399. 

Zahnle, K. and Sleep, N.H., 2002. Carbon dioxide cycling through the mantle and implications for the climate of the ancient Earth. In Fowler, C.M.R., Ebinger, C.J., and Hawkesworth, C.J. (eds) The Early Earth Physical, Chemical and Biological Development. Geol. Soc. Lond. Spl. Publ., 199, 231-57. 

Chemical evolution concerns the chemical processes that occurred on the ancient Earth about 4.5-3.5 million years ago. It is important to note that it preceded biological evolution that resulted in the formation of protocells. These forerunners of today s living cells were capable of self-reproduction at the expense of some protometabolism. After Oparin s ideas of the origin of life became widely known and especially after Stanley Miller reported his prebiotic soup experiments in 1953, the concept of chemical evolution became accepted. 

Living matter consists of six indispensable elements, namely C, H, O, N, P, and S, and, in addition, many more trace elements, for instance, iron. These elements are capable of existing in different valence states and are thought to have predominated the ancient Earth. 

The catalytically active, Wyoming-type montmorillonites are inferred to have developed their distinctive, high-Na smectite-rich compositions following deposition of granitic volcanic ash into a shallow, saline ocean during the Late Cretaceous. Oxygen isotopic data from Hadean zircons have been interpreted as indicating that oceans may have been present on the Earth by as early as 4,300-4,400 million years ago (62-63). While current evidence provides no information on the composition of the hypothesized Hadean seawater, the existence of oceans on the Hadean Earth is a necessary environment on the ancient Earth if catalytically active montmorillonites formed. 

I am now ready to discuss the ancient Earth. At a time when the ocean was anoxic and constrained little sulfate, the oceanic crust was not a significant oxygen sink. There was little sulfate in the circulating seawater to react with the basalt and no oxygen to oxidize vented sulfides. 

Figure 11 Biomolecules on the Ancient Earth. Reference Appendix 2, Explanations to the...

The interrelationship of ancient unicellular prokaryotes to UV irradiation and calcitriol-Uke molecular metabolism is unknown. UV-Ught might have induced genomic activation (such as an elementary Hh-Uke cascade for accelerated replication), and calcitriol-Iike protective mechanisms for survival. In comparing the atmospheric conditions of the ancient Earth with the Martian situation in terms of the effects on unicellular organisms in their hydrated, metabolically active, frozen, or dried state, UV-irradiation induced mutations, DNA-repair, and resistance mechanisms [1209]. 

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