Download Lecture13

Geobiology
Carbon-the basis of life
Microbes
Life in extreme environments
Origin of life on earth
Origin of the atmosphere
Astrobiology...
Where do we find Carbon?
•
•
•
•
•
•
•
•
Present in all living things
Diamonds and graphite
Calcium carbonate (limestone)
Oil
Coal
Atmosphere (CO2)
Meteorites
Volcanic eruptions
Carbon
Carbon
Sea creatures get C
from the ocean water to
make CaCO3
(carbonate)
Ooze fun facts
Sediment with >30% organic matter
Carbonate ooze: 48% of the ocean floor
Accumulates: 5 cm/1000 years
50 meters per million years
Dissolves at depths > 4.5 km
Foraminifera-carbonate shell
Ocean Thermometers!
(this guy is < 1 mm wide)
Carbon
Shells and coral and
carbonate ooze forms
limestone
Siliceous ooze
Plankton with silica shells
Covers 15% of the ocean floor
Makes chert
Carbon
Diatoms are algae with a silica shell...
45% of the total production of biomass from CO2 in the
ocean water
Carbon
Radiolaria are another algae with a silica shell...
Chewy carbon center with a silica coating
Chert
Made from radiolaria
Ooze Summary
• Ooze is plankton with shells of:
-Carbonate: Foraminifera
-Silica:
Diatoms and Radiolaria
• Ooze pulls carbon out of the water.
• When buried and heated, it can form PETROLEUM
Microbes
•
•
•
•
Used to make bread and beer
Yogurt and cheese
Antibiotics
Minerals such as pyrite or magnetite
Microbes are everywhere
Single-celled organisms:
Bacteria, fungi, algae, protozoa
Intracellular production of
iron minerals is an example
of direct precipitation.
Bacteria
Microbe cell wall
Extracellular precipitation
of calcium carbonate is an
example of indirect
precipitation.
Bacteria
Microbe cell wall
Modern stromatolites
Ancient stromatolites
grow in the intertidal zone. form columns.
Modern stromatolites
Ancient stromatolites
grow in the intertidal zone. form columns.
A cross section reveals
layering similar to that seen
in ancient stromatolites.
Modern stromatolites
Ancient stromatolites
grow in the intertidal zone. form columns.
A cross section reveals
layering similar to that seen
in ancient stromatolites.
Microbes live on the
surface of the stromatolite.
Sediment is deposited
on the microbes,...
...which grow
upward through
the sediment,
forming a new
layer.
Life in Extreme Environments
•
•
•
•
High Temperature
High Acidity (low pH)
High Salinity
Low Temperature
Thermophiles like it hot
Acidophiles like acidic
water
• pH can be as low as 1
• They turn mine drainage
into sulfuric acid
Halophiles like it salty
Iceworms like it chilly
These live in frozen
methane
Origin of Life
• The Life in a Flask experiment
• The Murchison Meteorite
• Early earth had minimal oxygenmostly CO2
Origin of Life
• Oldest microbes are 3.5 Ga
• Only microbes for 1 billion years!
Earth’s Atmosphere #1
• Earth’s first atmosphere was H and He
• Heat from sun and magma drove it away
Earth’s Atmosphere #2
• 4.4 Ga
•
•
•
•
Volcano erupts gases
Gases = CO2, some N, some H2O
After cooling, CO2 went into oceans
Carbonate deposition
Atmosphere #3
• Cyanobacteria (3.3 Ga to 2.7 Ga)
• Photosynthesis produces Oxygen (O)
• Early O reacts with Fe in oceans to form
Iron oxide minerals
• When Fe is gone, excess O goes into
atmosphere
Cambrian Explosion
• At 540 Ma there was an explosion of life
• Related to rise in oxygen in atmosphere?
Early animals: Hallucigenia
Diversity of organisms
800
429 Ma
Mass
extinction
End-Permian
mass extinction
364 Ma
Mass
extinction
600
400
End-Cretaceous
mass extinction
Cambrian
radiation
200
208 Ma
Mass extinction
0
600
400
200
Age (Ma)
0
Geologic Time Scale
• Boundaries of Geologic Time are related
to extinction events
4560 Ma
Earth and
planets
form
4510 Ma
Moon
forms
4000 Ma
Oldest
continental
rocks
4000
3500 Ma
Record of magnetic field
Fossils of primitive bacteria
3000
2000
1500
1000
500
Mass extinctions
359 Ma 251 Ma 200 Ma
65 Ma Present
Geologic Time Scale
• Precambrian (4.6 Ga to 540 Ma)
• Paleozoic (540-250 Ma)
• Mesozoic (250-65 Ma)
– Triassic
– Jurassic
– Cretaceous
• Cenozoic (65 Ma to the present)
Extraterrestrial Life?
To have life, we need water
Drainages on Mars:
Mars
Earth
Martian Meteorite
Martian bacteria?
ET life?
The Drake equation states that:
N = R* X fp X ne X fℓ X fi X fc X L
where:
N is the number of civilizations in our galaxy with which we might hope to be able to
communicate;
and
R* is the average rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is the average number of planets that can potentially support life per star that has planets
fℓ is the fraction of the above that actually go on to develop life at some point
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of civilizations that develop a technology that releases detectable signs of
their existence into space
L is the length of time such civilizations release detectable signals into space.