Origin of the Earth and of Life

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Chapter 10 Origin of the Earth and of Life
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Geological Scale 1 billion 109 years -
1 million 106 years age of universe
roughly 12 b. y. age of solar system 4.6 b.
y. age of earth 4.5 b. y. age of human-like
species 4 m. y. only!!! Recall geologic time
is divided into intervals broadest level of
division eons, subdivided into eras,
broken-down into periods, further split into
epochs.
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Four Eons Hadean 4.6 - 3.8 by Archean 3.8 -
2.5 by Proterozeic 2.5 - 0.54 by Phanerozoic
0.54 - present First three - Precambrian
Period Fourth - Cambrian Period gt abundance of
shelly fossils
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Contrast with events mentioned in Chapter
1 (1) K-T transition (extinction of
dinosaurs) only 65 mya (2) Pleistocene
Glaciations a mere 2 mya approximately!!
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Formation of Solar System 1. WHEN Universe
roughly 12 b. y. (estimate based on rate of
expansion) Earth rest of solar system formed
4.6 b. y ago human-like species have been in
existence since 4 m. y.
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Formation of Solar System 2. HOW (a) solar
nebula (b) planets inner planets Mercury,
Venus and Mars then Earth (of
course!) outer planets Jupiter, Saturn,
Uranus and
Neptune (the giant planets) animation
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Formation of Solar System Two
important formation for Earth 1. Jupiter
2. Moon
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Formation of Atmosphere and Ocean 1.
HOW impact degassing release of H2O and other
volatile
compounds Atmosphere and oceans should have
formed as the earth was forming, and formed by
direct impact 2. WHAT composition of early
atmosphere Some (lots?, greenhouse effect and
lots of steam?) of carbon dioxide (CO2) water
(H2O ) and probably very little oxygen (O2,
certainly free) and ozone (O3) but most likely
nitrogen (N, very stable) concentration about
what is today
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How much CO2 in early atmosphere?
Oxidation is an irreversible process
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How much O2 in early atmosphere?
Photolysis ? OH H and CO O H escapes But
this also means that 2 H2 O2 ? 2H2O 2CO O2 ?
2CO2 So free O2 gets depleted
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