the essential cosmic perspective chapter 7.5: earth as...
TRANSCRIPT
18-Apr-14
1
The Essential Cosmic PerspectiveChapter 7.5: Earth as Living Planet
Dr. Regina Jorgenson
18-Apr-14
2
18-Apr-14
3
WARNING:14,000 feet feels
different!
To see original MOV file, click here
18-Apr-14
4
18-Apr-14
5
Outline• What unique features of Earth are
important for life?
• How is human activity changing ourplanet?
• What makes a planet habitable?
What unique features of Earthare important for life?
(compare & contrast with Venus and Mars)
1) Surface liquid water
18-Apr-14
6
Venus & Mars:NO surface liquid water
T = 461CT = -50C
2) Atmospheric Oxygen
18-Apr-14
7
Question: Suppose that allphotosynthetic life (i.e. plants) died out.What would happen to all the oxygen in
our atmosphere?Could animals, including us, survive?
3) Plate Tectonics
>12 plates, moving at ~few cm per year (fingernail speed)
18-Apr-14
8
millions of years agoTo see original MOV file, click here
Question: If the motions of one plate relativeto another is 1 cm per year, how long would it
take for 2 continents 3000 km apart tocollide?
• 1) 30,000 years
• 2) 3,000,000 years
• 3) 300,000,000 years
• 4) 3,000,000,000 years
18-Apr-14
9
Question: If the motions of one plate relativeto another is 1 cm per year, how long would it
take for 2 continents 3000 km apart tocollide?
• 1) 30,000 years
• 2) 3,000,000 years
• 3) 300,000,000 years
• 4) 3,000,000,000 years
How many cm in3,000 km?
1 km = 105cm =100,000 cm
3,000 km = 3,000 x 105 cm = 3 x 108 cm = 300,000,000 cm
Subduction: plate material returning tomantle
Crust creation and recycling!
18-Apr-14
10
America andEurope are
moving apartby 3cm per
year = 30 kmper million
years. Thiscontinental driftis measured by
GPS.
Earth:Cold rigid crust that
breaks up
Venus:Hot plastic crust thatdoes not breaks up
No plate tectonics onVenus
4) Climate Stability
Venus: Too hot!(runaway greenhouse)
Mars: Too cold!(lost atmosphere)
18-Apr-14
11
4) Climate Stability
Earth: Just right! (Goldilocks planet)(runaway greenhouse)
Question: Considering changing Sunconditions -- the Sun has brightened 30%
over the past 4 billion years -- how was theEarth able to maintain long-term climate
stability?
• 1) We got lucky
• 2) The Earth’s orbital radius increased
• 3) The size of the Earth increased
• 4) The carbon dioxide cycle
Question: Considering changing Sunconditions -- the Sun has brightened 30%
over the past 4 billion years -- how was theEarth able to maintain long-term climate
stability?
• 1) We got lucky
• 2) The Earth’s orbital radius increased
• 3) The size of the Earth increased
• 4) The carbon dioxide cycle
18-Apr-14
12
Carbon Dioxide Cycle (CO2
Cycle)a.k.a. Earth’s long-term thermostat
Carbon Dioxide Cycle (CO2
Cycle)a.k.a. Earth’s long-term thermostatRate dependent on temperature
Temperatureincreases
moreevaporation/ra
infall
less CO2 inatmosphere
lessgreenhouse
effect
Temperaturedecreases
Temperaturedecreases
lessevaporation/ra
infall
more CO2 inatmosphere
moregreenhouse
effect
Temperatureincreases
Question: Let’s recap! Which fourunique features of Earth are
important to life?
• 1) surface liquid water, oil, atmospheric Oxygenand CO2, plate tectonics
• 2) surface liquid water, Oxygen, CO2, dinosaurs
• 3) surface liquid water, atmospheric Oxygen,plate tectonics, climate stability
• 4) pizza, the internet, iphones, beer
18-Apr-14
13
Question: Let’s recap! Which fourunique features of Earth are
important to life?
• 1) surface liquid water, oil, atmospheric Oxygenand CO2, plate tectonics
• 2) surface liquid water, Oxygen, CO2, dinosaurs
• 3) surface liquid water, atmospheric Oxygen,plate tectonics, climate stability
• 4) pizza, the internet, iphones, beer
How is human activitychanging our planet?
• There are historicalclimate changes thatoccur “naturally” dueto things like smallcyclical changes inEarth’s axis tilt ormajor volcanicreleases of CO2.
•leads to ice ages(every 10,000 yearsor so)
18-Apr-14
14
Global Warming
Global average temperature increased 0.8 C in pastcentury
What is causing globalwarming?
The Greenhouse Effect
greenhouse gases
are:
methaneCO2
water vapor
18-Apr-14
15
The Greenhouse Effect
greenhouse gases
are:
methaneCO2
water vapor
Note! Greenhouse Effectis crucial for life! But toomuch of a good thing can
be bad... i.e. Venus
Proof? We see thegreenhouse effect on other
planets
CO2 levels today are higher than atany point in the past 400,000 years
18-Apr-14
16
Temperature variation
CO2
Thousands of years ago
Temperature variation
CO2
Thousands of years ago
Question:What do you see when you compare these graphs?
Temperature variation
CO2
Thousands of years ago
Answer:Periods of higher CO2 concentration correspond
with periods of higher global average temperature
18-Apr-14
17
Discussion Question:Imagine you are a scientisttasked with determining the
Earth’s temperature and CO2
levels 400,000 years ago.How would you do this?
Ice Cores!
Similar to tree rings,ice layers are a
record of the past
18-Apr-14
18
CO2 levels correlate with temperature
Discussion Questions
18-Apr-14
19
Discussion Questions
Can you explain whatthis graph is showing?
Discussion Questions
What could be causing theincrease in CO2 levels over
the past 50 years?
Discussion Questions
Bonus points: Can youexplain the detailed
behavior of the data?(i.e. the red line)?
18-Apr-14
20
Alps, January 2004 Alps, June 2004
Effects of Global Warming?
Melting polar ice caps & Melting ice sheets
Greenlandwhite = year round ice sheet
orange = melt region
18-Apr-14
21
sea level rise of 1 metercould occur within the centurysimply from heating of water
FLOODING:
What makes a planethabitable?
Size Matters: Which coolsfaster?
12
3
18-Apr-14
22
PlanetarySize
Small
Large
relative sizes
Mercury Venus Earth Mars
Transit of Venus: June 5, 2012
18-Apr-14
23
Distance from Sun
18-Apr-14
24
Hot core enabled magneticfield
Magnetic field protects Earth fromharmful solar particles and creates
aurora borealis
To see original MOV file, click here
18-Apr-14
25
Now you are a scientist taskedwith locating other Earth-like
planets where human lifecould possibly exist.
How would you do this?
Search for extra-solar planets
Kepler Space Telescope
18-Apr-14
26
CO2 levels correlate with temperature