Download Rocky Planets The formation of our Moon The Nature of

Review: Rocky
Planets 2
Moon Formation
Homework Due Friday Morning 9am
Today in class
Matter
Fundamentals
Atoms
Elements
Ages of Rocks
I
Review: Rocky Planets
I
The formation of our Moon
I
The Nature of Matter
I
The Age of Earth (and the solar system)
Radioactive Decay
Potassium-40
Age of Earth
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
Review: Rocky Planets 2
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Question concepts
Review: Rocky
Planets 2
Question #1: While no liquid water currently exists on
Mars’ surface, long-lived liquid water existed on the surface
in the distant past.
Moon Formation
Question #2: On Earth, the carbon dioxide content of the
atmosphere is regulated to give a stable greenhouse effect
because more carbon dioxide leads to more water in the
atmosphere and thus more formation of carbonate rocks.
This removes the excess carbon dioxide from the
atmosphere, bringing it back to equilibrium.
Ages of Rocks
Question #3: Among the rocky planets, Earth is the only to
exhibit plate tectonics. Others exhibit some evidence of
volcanoes, craters, and erosion (typically by wind).
Matter
Fundamentals
Atoms
Elements
Radioactive Decay
Potassium-40
Age of Earth
Review: Rocky
Planets 2
Moon Formation
Matter
Today in class
I
The formation of our Moon
I
The Nature of Matter
I
The Age of Earth (and the solar system)
I
Radioactive Decay
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Giant Impact formation of our Moon
Problems with Moon formation:
I Too large to be captured from
other orbit
I Too low density to have
formed with Earth
The Clue: Composition of most of
the Moon very similar to the outer
layers of the Earth
The hypothesis:
I Mars sized planetesimal
impacted Earth after it had
differentiated, blasting off
outer layers.
I Material that stayed in Earth
orbit coalessced to form
Moon,
I All debris was accreted or
ejected.
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Review: Rocky
Planets 2
Moon Formation
Matter
Question concepts
Fundamentals
Atoms
Elements
Ages of Rocks
Question #4: A major motivation for the giant impact
scenario for the formation of the Moon is the similarity of
the Moon’s composition to the outer layers of the Earth.
Radioactive Decay
Potassium-40
Age of Earth
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
The Nature of Matter
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Fundamental components of matter
quarks
up
down
Review: Rocky
Planets 2
Moon Formation
electron
Matter
Baryons:
uud
proton
udd
neutron
Electrons:
I
negative electrical charge
I
very small mass (1/2000 of proton or neutron)
Protons and Neutrons (Baryons)
I
Made of quarks
combinations of up and down quarks
I
positively charged
I
most mass of matter
I
make up atomic nucleus
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Nuclei and Atoms
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Review: Rocky
Planets 2
Moon Formation
Matter
Question concepts
Fundamentals
Atoms
Elements
Ages of Rocks
Question #5: The nucleus of an atom is very small
compared to its overall size. The size comes mostly from the
region over which the electon ”cloud” is spread.
Radioactive Decay
Potassium-40
Age of Earth
Elements and Isotopes
I
Elements have
different chemical
properties due to
different number of
protons (and
therefore electrons)
I
Name of an
element is just an
alias for how many
protons it has (see
periodic table)
I
A given element
can have several
different numbers
of neutrons – called
different isotopes.
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Question concepts
Question #6: The name of an element is related to the
number of protons in the nucleus. This is the number that
increases one by one left-to-right and top-to-bottom on the
periodic table. This is also the number of electrons that an
atom of this element generally has, and determines the
chemical properties of the element.
Question #7: The name of an element is related to the
number of protons in the nucleus. The total number of
protons and neutrons is indicated by saying a number after
the name. For example, carbon-14 (also written 14 C) has 6
protons and 8 neutrons for a total of 14 protons and
neutrons.
Question #8: The name of an element is related to the
number of protons in the nucleus. The total number of
protons and neutrons is indicated by saying a number after
the name. For example, carbon-14 (also written 14 C) has 6
protons and 8 neutrons for a total of 14 protons and
neutrons.
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
How do we measure the age of a Rock?
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
How do we measure the age of a Rock?
Radioactive Decay!
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Radioactive Decay
Review: Rocky
Planets 2
Radioactive decay arises through changes in the particles in
the nucleus. Changes in the number of protons and neutrons.
electron
Moon Formation
Matter
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Carbon−14
Nitrogen−14
half-life: The amount of time for half of a material to decay
easily measured and not effected by temperature, etc
for Carbon-14, half-life is 5730 years.
Potassium-40 decay
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Why Potassium-40? (19 protons, 21 neutrons, 21
19 K)
I half-life 1.25 billion years (decent fraction of Earth age)
I decay product Argon-40 (18 protons, 22 neutrons, 22 Ar)
18
is an non-reactive gas (can’t form into rock)
I Any Argon-40 in a rock must come from Potassium-40
decay
decay of potassium-40 is also the largest source of radiation
in your body
Review: Rocky
Planets 2
Moon Formation
Matter
Question concepts
Fundamentals
Atoms
Elements
Ages of Rocks
Question #9: Argon is an example of a material that does
not become part of rocks when they form because it is a
non-reactive gas rather than a solid.
Radioactive Decay
Potassium-40
Age of Earth
Age of Earth
Review: Rocky
Planets 2
Moon Formation
Matter
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth
Oldest rocks on Earth are about 4 billion years old, with the
oldest small grains around 4.4 billion years old.
Oldest rocks on the Moon are also about 4.4 billion years old
Oldest rocks in the solar system (recovered meteorites) are
about 4.55 billion years old
- leftovers of material that formed the rocky planets
Review: Rocky
Planets 2
Moon Formation
Question concepts
Question #10: A rock can be dated by comparing the
amount of a radioactive isotope to the amount of its decay
product in the rock. The amount of the first isotope
decreases over time and the amount of the product
increases. At the half-live there is an equal amount of
radioactive and product material.
Matter
Fundamentals
Atoms
Elements
Ages of Rocks
Radioactive Decay
Potassium-40
Age of Earth