Transcript Goldilocks Problem

The Goldilocks Problem?
Astronomical!
The Goldilocks Problem?
Why is Venus so hot…
and Mars so cold…
and Earth just right….?
Thought Question
What is the main reason why Venus is hotter
than Earth?
A.
B.
C.
D.
E.
Venus is closer to the Sun than Earth.
Venus is more reflective than Earth.
Venus is less reflective than Earth.
Rain stopped, but volcanoes didn’t
Human activity has led to declining temperatures on
Earth.
Thought Question
What is the main reason why Venus is hotter
than Earth?
A.
Venus is closer to the Sun than Earth.
# 1 Answer given by most people…
and it’s not correct!
Thought Question
What is the main reason why Venus is hotter
than Earth?
A.
B.
C.
D.
E.
Venus is closer to the Sun than Earth.
Venus is more reflective than Earth.
Venus is less reflective than Earth.
Rain stopped, but volcanoes didn’t
Human activity has led to declining temperatures on
Earth.
Thought Question
What is the main reason why Mars is no longer
considered habitable (on its surface)
A.
B.
C.
D.
E.
Mars is farther from the Sun than Earth, and too
cold
Mars doesn’t have a thick atmosphere
Mars’ volcanoes stopped erupting
The greenhouse effect is not as strong on Mars
compared to Earth.
Martians screwed up the climate long ago.
Thought Question
What is the main reason why Mars is no longer
considered habitable (on its surface)
A.
Mars is farther from the Sun than Earth, and too
cold
# 1 Answer given by most people…
and it’s not correct!
Thought Question
What is the main reason why Mars is no longer
considered habitable (on its surface)
A.
B.
C.
D.
E.
Mars is farther from the Sun than Earth, and too
cold
Mars doesn’t have a thick atmosphere
Mars’ volcanoes stopped erupting
The greenhouse effect is not as strong on Mars
compared to Earth.
Martians screwed up the climate long ago.
Carbon Dioxide Cycle
•
Terrestrial Planets
can “Recycle” CO2
from atmosphere
to crust to
atmosphere over
time
•
Estimate ~25
million years or
more for this to
occur on Earth
Carbon Dioxide Cycle
•
How do
atmospheres of
Venus & Mars
differ in their
ability to cycle
CO2 from
atmosphere to
crust and
back??
Venus in UV light
Venus mapped with Radar
The surface of Venus
Venus’ surface
Venera Probes from 1970’s survived for
minutes…
Venus’ surface
Venera Probes from 1970’s survived for
minutes…
Why is Venus so hot?
Venus’ Atmosphere
•What is it made of?
•How does it change in height?
•How does it circulate?
Atmosphere of Venus

Venus has
very thick
carbon dioxide
atmosphere with
surface pressure
90 times larger
than Earth.
Atmosphere of Venus

Reflective clouds
contain droplets of
sulfuric acid.

The upper
atmosphere has
fast winds that
remain
unexplained.
Venus’
Atmosphere
Venus’ Atmosphere
Sun’s UV light disassociates
H20 at this height!
Water condenses into clouds,
allowing for rain around 0 C
Greenhouse Effect on Venus

Thick CO2
atmosphere
produces an
extremely strong
greenhouse effect.

Earth escapes this
fate because most
of its carbon and
water are in rocks
and oceans.
Why is Venus so hot?
The greenhouse effect on Venus keeps its
surface temperature at 470°C.
But why is the greenhouse effect on Venus
so much stronger than on Earth?
Runaway Greenhouse Effect
More evaporation,
stronger greenhouse effect
Greater heat,
more evaporation

The runaway greenhouse effect would account
for why Venus has so little water.
Explaining Venus’ Atmosphere
•Lots of Volcanoes
•CO2, H2S04 are outgassed
•CO2 traps infrared heat from Sun
•Atmosphere heats up
•Water can’t condense => No Rain!
Carbon Dioxide Cycle
•
“Recycle” CO2
from atmosphere
to crust to
atmosphere over
time
•
Estimate ~25
million years or
more for this to
occur on Earth
Carbon Dioxide Cycle
•
How do
atmospheres of
Venus & Mars
differ in their
ability to cycle
CO2 from
atmosphere to
crust and
back??
Carbon Dioxide Cycle
•
Assume all 3 planets
had similar compositions
and conditions “early” in
the solar system’s
history…
•
Assume all 3 had liquid
water, active volcanoes,
and CO2 in atmosphere
Carbon Dioxide Cycle
Step 1: Evaporation/Rain
1
•
Liquid water evaporates
•
Condenses into clouds
in lower atmosphere
•
Rain falls through
atmosphere forming
Carbonic Acid (H2CO3)
 CO2 gas is absorbed
Aside – what does Coca Cola
have to do with Astronomy?
Aside – what does Coca Cola
have to do with Astronomy?
Aside – what does Coca Cola
have to do with Astronomy?
Water & CO2…
•
How do you fill lots of
bottles with syrup quickly?
•
PUSH it in with a
propellant
•
CO2 is a good choice!
•
People like the bubbles!
Carbon Dioxide Cycle
Step 2: Mineral Erosion by Acid Rain
•
•
2
Carbonic Acid (H2CO3)
in rivers erodes rocks
Carbon Dioxide Cycle
Step 2: Mineral Erosion by Acid Rain
•
Carbonic Acid (H2CO3)
in rivers erodes rocks
•
Carbonate (CO32-) ion
picked up in minerals
washed to ocean
•
Calcium easily absorbed
2
 CO2 is carried to oceans
Carbon Dioxide Cycle
Step 3: Tying Carbon into Rocks &
Life!
3
•
Calcium from rocks
forms CaCO3 (Calcium
Carbonate)
•
CaCO3 = Limestone
•
CaCO3 = Coral, Mollusk
shells!
 CO2 accumulates on
seafloor
Carbon Dioxide Cycle
Step 3: Tying Carbon to Rocks & Life!
Carbon Dioxide Cycle
Step 4: Tectonics & Subduction!
4
•
Tectonics gradually pulls
seafloor down
•
CaCO3 broken back into
CO2 & other minerals
 CO2 now inside crust
Carbon Dioxide Cycle
Step 5: Volcanic Outgassing!
Carbon Dioxide Cycle
Step 5: Volcanic Outgassing!
•
5
Eventual Volcanic
Activity pushes CO2
back into atmosphere
 CO2 now in
atmosphere again!
Carbon Dioxide Cycle
Venus Feedback Loop Failure

1
5
Too Hot for
clouds to form
low enough
But…
 Volcanoes
don’t stop!
Carbon Dioxide Cycle
Venus Feedback Loop Failure
•
1
•
•
•
No Rain
NO CO2 gas
absorbed
More CO2 added!
Runaway
Greenhouse Effect!
Mars
Schiaparelli’s “Canals”
“The Face” :
Is just an illusion…
More illusions:
Pyramids
Happy Faces!
What is real?
A Martian Sunset…
Mars vs. Earth
50% Earth’s radius, 10% Earth’s mass
 1.5 AU from the Sun
 Axis tilt about the same as Earth
 Similar rotation period (25 hours/”day”)
 Thin CO2 atmosphere: little greenhouse
effect

=>Main difference: Mars is SMALLER
Mars IS smaller…
And Earth has life!
Carbon Dioxide Cycle
Mars Feedback Loop Failure
Evaporation
•
Rain
•
CO2 gas flushed out
But…
•
Interior cools off
•
Volcanoes Stop!
•
1
5
Carbon Dioxide Cycle
Mars Feedback Loop Failure
•
Atmosphere CO2
decreases
•
Planet freezes
1
5
Why did Mars change?
Volcanoes…as recent as 180 million years ago…
Past tectonic activity…
Climate Change on Mars
No widespread
surface water for
3 billion years.
 Greenhouse
effect probably
kept surface
warmer before.
 Somehow Mars
lost most of its
atmosphere.

Climate Change on Mars
Climate Change on Mars

Magnetic field may have preserved early
Martian atmosphere.

Solar wind may have stripped atmosphere after
field decreased because of interior cooling.
Recent Polar Climate Change
Seasons on Mars

Seasons on Mars are more extreme in the
southern hemisphere because of its elliptical orbit.
Storms on Mars

Seasonal winds on Mars can drive huge dust storms.
What geological features tell us
water once flowed on Mars?
The surface of Mars appears to have ancient riverbeds.
Eroded
crater
The condition of craters indicates surface history.
Close-up of eroded crater
The Martian Surface Map
A *really* GRAND canyon…
A *even bigger* volcano
Differences in Hemispheres
Low-lying regions may once have had oceans.
Low-lying regions may once have had oceans.
Opportunity
Spirit
NASA’s SPIRIT & OPPORTUNITY Rovers…still sending data!
• 2004 Opportunity Rover provided strong evidence for abundant
liquid water on Mars in the distant past.
• How could Mars have been warmer and wetter in the past?
Today, most water
lies frozen
underground (blue
regions)
Some scientists
believe accumulated
snowpack melts
carve gullies even
today.
Exploring Mars
Winds on Mars
Wind trails
from “dust
devils”
Rivers on Mars
… & Earth!
… More
evidence
of water