EESC 2500 Archean Eon

Hadean Eon

• 4.0 - 4.6 billion years ago

• Earth form

• No crust (crust form and go)

Archean Eon

• 4.0 - 2.6 Billion Years Ago

• Formation of crust

• Formation of first ocean

• Life first appear and evolve

Early Atmosphere

• Reducing atmosphere “no free oxygen”

• Mostly CO2, H2, H2O and N2 from volcanoes

Key molecules during Early Atmosphere

• Ammonia (NH3) and Methane (CH4)

• Created from large asteroid impacts

• Important building blocks for life

How is the key molecules form

• large astroid impact

Miller-Urey Experiment

Goal: to test if building block can form in Earth’s early atmosphere

Method: stimulate early atmosphere (CH4, NH3, H2) and ocean + adding energy like lightning

Results:

• produced 20 amino acid

• Prove that organic molecules can form from inorganic materials

Coacervate

• Tiny sphere formed when lipid clumps together in water

• Act as proto-cells

Why is Porto-cell important?

• It can trapped organic molecules inside

• Important steps towards first true cells

LUCA (Last Universal Common Ancestor)

• Not the first life

• Single-cell organism

• Current life on Earth descended from

Characteristic of LUCA

1) Anaerobic

2) Thermophilic

3) H2 dependent

4) CO2 and N2 fixing

Anaerobic

Do not need oxygen

Thermophilic

Heat resistance

H2 dependent

Used hydrogen gas for energy

CO2 and N2 fixing

Used CO2 and N2 to build molecules

LUCA’s home

• lived at anaerobic hydrothermal vents on the sea floor

• Existed 4.5 billion years ago

The first life

Archaea

Archaea

• first life

• Single-cell organism

• No nucleus

• Genetically and metabolismally different from bacteria

Key feature of Archaea

• cell membrane are made of different type of fat

• More stable in extreme environment

Methanogenesis

organism that produce methane as waste product

Ex: Archaea

Why early life stay at Hydrothermal vents?

• provide chemical energy, warmth and shelter

Chemoautotrophy

Organism gets energy by breaking down inorganic chemicals

What is the earliest life form?

Heterotrophs

Heterotrophs

• earliest life form

• consume organic molecules for food because they couldn’t make their own

Anoxygenic Photosynthesis

• bacteria evolves

• Used sunlight for energy without producing oxygen

• Used chemical like hydrogen sulfide or iron instead of water

Banded Iron Formation (BIF)

Bacteria oxidized iron using sunlight

Why is it hard to find evidence of early life?

• Hadean rocks are gone

• Archean rocks are deformed and metamorphosed

• Fossil destroyed

Key rocks formation

• Acosta Gnesis

• Isua Supracrustal Belt

• Strelley Pool Formation

Acasta Gnesis

• 3.96 Ga

• Oldest known rock

• Metamorphosed

• Cannot contain fossil

Isua Supracrustal Belt

• 3.8 - 3.7 Ga

• Contain Banded Iron Formation that prove hydrothermal activity

• Carbon isotopes evidence that life prefer lighter carbon (Carbon-12)

• Possible Stromatolites (microbial mats)

Stroller Pool Formation

• 3.4 Ga

• Contain oldest fossil evidence

• Stromatolites

• Carbon isotopes (light carbon)

What is Earth’s Protective Shield?

The Magnetic Field

Magnetic Field

• Earth protective shield

• Generate by the movement of molten iron in Earth’s outer core

When did Magnetic Field started?

3.45 billion years ago

Why is Magnetic Field important?

• Create magnetosphere

• Block solar wind

• Protect atmosphere from being stripped away