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Assembling LifeHow Can Life Begin on Earth and Other Habitable Planets?$
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David W. Deamer

Print publication date: 2019

Print ISBN-13: 9780190646387

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780190646387.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 26 October 2021

The Early Earth: An Ocean with Volcanoes

The Early Earth: An Ocean with Volcanoes

Chapter:
(p.1) 1 The Early Earth: An Ocean with Volcanoes
Source:
Assembling Life
Author(s):

David W. Deamer

Publisher:
Oxford University Press
DOI:10.1093/oso/9780190646387.003.0006

Malcolm Walter was talking about the Pilbara region of Western Australia where some of the oldest known biosignatures of ancient life, in the form of extensive fossilized stromatolites, are preserved. The first potential stromatolite was discovered by graduate student John Dunlop, who was studying barite deposits at the North Pole Dome. Roger Buick went on to investigate the biogenicity of the stromatolites for his PhD (Buick, 1985) and Dunlop, Buick, and Walter published their results (Walter et al., 1980). In a prescient paper, Walter and Des Marais (1993) proposed that the ancient stromatolite fossils could guide the search for life on Mars. I have walked with Malcolm Walter through the Dresser formation where the fossils were found. It is humbling to realize that if time passed at a thousand years per second, it would take 41 days to go back in time to the first signs of life on our planet. In any description of events that occurred some 4 billion years ago, certain assumptions must be made. I will try to make assumptions explicit throughout this book, beginning here with the geochemical and geophysical conditions prevailing on the early Earth and Mars. I am including Mars not as an afterthought but because both planets had liquid water 4 billion years ago. Most of our understanding of planetary evolution comes from observations of our own planet, but it is now clear that the Earth and Mars were undergoing similar geophysical processes during the first billion years of the solar system’s existence, with an equal probability that life could begin on either planet. In a sense, the surface of Mars is a geological fossil that has preserved evidence of what was happening there at the same time that life began on the Earth. For instance, Martian volcanoes offer direct, observable evidence that volcanism was occurring nearly 4 billion years ago; making it plausible that similar volcanism was common on Earth even though the evidence has been completely erased by geological and tectonic processes.

Keywords:   Apollinaris Mons, Cerium, Hadean atmosphere, Malcolm Walter, Pilbara region, biogenic elements, fugacity, geyserite, molecular clouds, planetesimals

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