Transcript Rare Earth Hypothesis

Rare Earth Hypothesis
That occurrence of Earth-like
planets with complex life forms
in the universe is rare.
• So many geologic and astronomical
conditions worked together to
create Earth-like environments.
• Complex life is not common.
Competing Theory: Principle of
Mediocrity
States that Earth-like planets are
common in the universe; so is
complex life.
• Earth is “mediocre” … not unique.
• Carl Sagan & Francis Drake
Which Theory is Accurate?
… More data is needed.
Planet Size & Mass
Average Mass
Star
Iron Core
Rare Earth
Hypothesis:
Conditions
needed to
support
complex life
Right Distance
from Sun
Atmosphere
Jupiter-like
Neighbor
Occasional
Catastrophes
Large
Moon
Large/Massive enough to have enough gravity to hold on to an atmosphere; Large
enough to maintain internal heat (needed for volcanism & plate tectonics)
Last long enough for
evolution. Massive
stars last only a few
million yrs.
Temperatures for
LIQUID WATER
Planet Size & Mass
Average Mass
Star
Iron Core
Rare Earth
Hypothesis:
Conditions
needed to
support
complex life
Right Distance
from Sun
Cause mass
extinctions that
stimulate EVOLUTION.
New species can be
successful and
diversify.
Occasional
Catastrophes
Creates a magnetic
field that protects
organisms from
dangerous solar wind.
Atmosphere
Jupiter-like
Neighbor
Large
Moon
Moon’s gravity pulls on Earth’s axis. This lessens the
amount that Earth WOBBLES on its axis. WOBBLING
results in CLIMATE CHANGE (Ice age > warming).
- Burns up
meteorites so they
don’t impact.
- Regulates temps.
- Filters out
dangerous
wavelengths of
energy (UV)
- Oxygen for life!
Large size = Large
gravity. Jupiter
attracts meteorites
that would otherwise
collide w/ inner
planets.