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Origin of Life
Reptiles,
M C Escher
Lecture Ten, Feb. 7, 2003
Course Project
• Topic of your choosing related to class.
• Proposal (1-2 pages) Feb. 14, 2003.
• Project background (3-5 pages) Mar. 28,
2003.
• Project (10 pages) April 25.
Pathfinder the Race to Mars
• 60 min video on web site.
• 1996 Mars Global
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•
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Surveyor lunched to orbit
and map Mars.
Also Mars Pathfinder with
its small rover.
These followed failed
Mars Observer in 1993.
See Manyrovers_full.jpg
(note, this is a 7.4 MB
image)
The Doomsday Asteroid
• 60 min Video
•
about impact of
comet Shoemaker
Levy 9 with Jupiter
and present day
threat from
impacts.
Keck Telescope
infrared images of
collision.
Hubble Image of Impact Plum
Impact site itself just out of site beyond rim
Gamma Ray Bursts
• The Nova program
Death Stars discusses
Gamma Ray bursts.
These are the most
energetic explosions
since the Big Bang.
They have now been
detected billions of
light years from
Earth.
Simulation of collapse
of giant rotating star to
produce two gamma
ray jets.
Project
• Almost any topic of interest to you and related
•
•
to the class is possible.
Try and discuss as much of the science, covered
in class, as possible.
Example of a project: “The Movie 2001 and The
Evolution of Man”, by C Horowitz. See paper
copy or class web site. You should read this
paper! Note, how it discusses the movie “2001
A Space Odyssey” in terms of many of the topics
covered in class.
Ideas for Projects
• Big Bang/ creation of Universe.
• Supernovae, neutron stars, and or black holes.
• Impacts of comets and asteroids.
– Death of dinosaurs (See for example, “T.Rex and the
crater of doom” by L. Alvarez).
– Impact of Shoemaker Levy 9 with Jupiter (See for
example, “Impact Jupiter” by D. Levy)
– Present day impact threat.
Project Ideas Continued
• Mars
– Robotic exploration
– Manned mission (See for example, “The Case For
Mars”, R. Zubrin)
– Colonization or terrafarming (See text)
• Discuss Science in a Science Fiction Story.
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2001, 2010… by A. C. Clark
“Andromeda Strain” by M. Crichton
“Red, (Green, Blue) Mars” by K. S. Robinson
Lots and Lots to chose from…
• Space exploration
Ideas Continued
• Origin of Life
• Extrasolar planets (see for example,
“Worlds Unnumbered” by D. Goldsmith)
• Interstellar Flight and Colonization.
• SETI
•…
Earth’s Thermostat
• Amount of CO2 in atmosphere controlled by
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•
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absorption to make carbonate rocks or outgassing from volcanoes.
This changes greenhouse effect and Earth’s
temperature.
Earth’s temperature has been remarkably stable
over its history despite an increase in the Sun’s
output.
There must have been more CO2 at early times
and this somehow decreased in a way that
compensated the increase in the Sun’s output.
Earth’s Atmosphere Over Time
We don’t understand this
Thermostat
• We don’t understand many of the mechanisms
•
•
•
which regulate CO2.
How much more CO2 will lead to a runaway
greenhouse effect such as what happened to
Venus?
What will the ultimate effect of human produced
CO2 be (global warming)?
How close did Earth come to losing CO2 and
going into a permanent global ice age
(“Snowball Earth”)?
Venus is Hot as Hell
• Atmosphere is 90
•
•
times thicker then
Earth and mostly CO2.
Greenhouse effect
raises temp. by 400 C
to about 470 C (hot
enough to melt lead).
Not a likely place for
life.
Mars was once Warmer and Wetter
• In the past, Mars
•
•
atmosphere had much
more CO2.
This allowed greenhouse
effect to raise temp.
above 0 C.
Mars has since lost most
of its atmosphere for
unknown reasons,
perhaps absorption in
rocks.
Earth is Geologically Alive.
• We are lucky that Earth’s core is still hot and this heat
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flow drives convection, plate tectonics and generates
magnetic field.
Plate tectonics may help regulate CO2 in atmosphere.
Note, no other planet in solar system appears to have
plate tectonics.
Earth’s temp. remained remarkably stable despite
warming Sun.
Timeline: Big Bang 13 Bya, creation of chemical
elements 12-5 Bya, formation of Earth 4.6 Bya,
formation of Moon in Big Whack 4.5 Bya, Large impact
basins on Moon 3.8 Bya, Origin of life 3.8 Bya.
Origin of Life According to
Michelangelo
Origin of Life
• According to Mel Brooks
• Real Media clip of creation of life from
Young Frankenstein
The Chemistry of Life
• Start with very simple chemicals such as
CO2, H2O, N2, NH3.
• Temperature and pressure allow liquid
H2O.
• Energy source: could be ultraviolet
radiation from Sun, Lightening, Chemical
reactions.
• Somehow produce the building blocks of
life.
Amino Acids: Building Blocks of Life
• Amino acids are chemical compounds with amine groups
•
(containing nitrogen, N) and weak acid groups (HO2C)
that can be linked together to form long chains called
proteins.
Example: Amino acid Alanine
H
H
N
H
C
O
C
O
Acid group
H
Amine group
H
C
H
H
Chemistry 101:
Note, 4 bonds
for C, 3 bonds
for N, 2 for O
and 1 for H
Chemistry 101
• Remember
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Hydrogen,
Carbon,
Nitrogen,
Oxygen,
Neon,
H 1 electron, 1 in outer shell
C 6 electrons, 4 in outer shell
N 7 electrons, 5 in outer shell
O 8 electrons, 6 in outer shell
Ne 10 electrons, 8 in outer shell
• Ne is a noble gas (unreactive) with a closed
•
electron shell.
Chemical bond (covalent bond): sharing of
electrons between two atoms.
Chemical bonds
• Atoms like to bond to form closed shells.
• C likes to form 4 bounds (4 shared electrons
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plus the 4 it starts with gives 8)
N likes to form 3 bounds.
O likes to form 2 bounds.
H likes to form 1 bound.
Draw bounds as single line (share one electron)
or double line for a double bound where two
electrons are shared.
Two amino
acids
H
N
C
H
O
C
H
Acid
group
N
C
O
H
C
Amine
group
H
C
H
H
H
C
O
H
H
O
H
H
H
H
• The amine group of one amino acid can react
with the acid group of another to produce a
molecule of H2O and the joining of the two.
These
react
to
form
H2O
H
O
C
N
O
H
C
H
H
H
C
C
H
H
O
O
H
C
H
H
H
N
H
N
H
C
H
C
H
H2O + O
H
C
N
Two amino acids
H
C
O
H
C
H
H
C
O
H
H
H
H
C
H
H
One longer chain that still has an amine and an acid group
Proteins are Made of Amino Acids
• Amino acids have an amine group (N) and an
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acid group (CO2H)
Can bind amino acids together to produce long
molecules called proteins.
Proteins form the basis for life on Earth.
Earth life uses proteins made from 20 different
amino acids strung together in definite orders.
Where did the amino acids come from?
How were they put together in the correct
order?
The Chemistry of Life
• Short real video clip about the chemistry
of life from the discovery channel.
Life made from 20 amino acids
Glycine
Valine
Alanine
Lysine
Note, carbons at ends of lines and hydrogens are not shown
Red is oxygen (acid) and blue is nitrogen (amine) group
A Protein
• To specify a unique protein you must specify
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which one of the 20 amino acids occurs first,
which amino acid occurs 2nd and so on.
A protein may be thousands of amino acids long.
Need a long string of thousands of numbers
each of which goes from 1 to 20.
Example 5-12-3-3-3-2-20-19-11-…
The Left Hand of God
• A given amino acid
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can come in two
mirror image forms.
Life on Earth only
uses the left handed
form.
We don’t understand
the origin of this
chirality (Greek word
for hand).
Miller Experiment
• Stanley Miller, a graduate
•
student of Harold Urey, in
1953 placed H2O, H2, NH3,
CH4 in a flask. Constantly
boiled and recondensed the
H2O and added an electrical
discharge (lightning) for
energy.
Spectacular results:
produced lots of amino
acids and other organic
compounds.
For next time
• Read chap. 4 of Jakosky about the earliest
life and read “Vital Dust", pages 1-23 in
course packet about origin of life.
• Think about your course project. Proposal
(1-2 pages) due Feb. 14, 2003.
• Next lecture, Monday Feb. 10, 2003, “Life
in a Bottle”.