The Essential Cosmic Perspective Chapter 7.5: Earth as Living Planet Dr. Regina Jorgenson
WARNING: 14,000 feet feels different!
To see original MOV file, click here
Outline What unique features of Earth are important for life? How is human activity changing our planet? What makes a planet habitable?
What unique features of Earth are important for life? (compare & contrast with Venus and Mars)
1) Surface liquid water
Venus & Mars: NO surface liquid water T = -50C T = 461C
2) Atmospheric Oxygen
Question: Suppose that all photosynthetic 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
millions of years ago To see original MOV file, click here
Question: If the motions of one plate relative to another is 1 cm per year, how long would it take for 2 continents 3000 km apart to collide? 1) 30,000 years 2) 3,000,000 years 3) 300,000,000 years 4) 3,000,000,000 years
Question: If the motions of one plate relative to another is 1 cm per year, how long would it take for 2 continents 3000 km apart to collide? 1) 30,000 years 2) 3,000,000 years 3) 300,000,000 years 4) 3,000,000,000 years How many cm in 3,000 km? 1 km = 105cm = 100,000 cm 3,000 km = 3,000 x 105 cm = 3 x 108 cm = 300,000,000 cm
Crust creation and recycling! Subduction: plate material returning to mantle
America and Europe are moving apart by 3cm per year = 30 km per million years. This continental drift is measured by GPS.
Earth: Cold rigid crust that breaks up Venus: Hot plastic crust that does not breaks up No plate tectonics on Venus
4) Climate Stability Venus: Too hot! (runaway greenhouse) Mars: Too cold! (lost atmosphere)
4) Climate Stability Earth: Just right! (Goldilocks planet)
Question: Considering changing Sun conditions -- the Sun has brightened 30% over the past 4 billion years -- how was the Earth 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 Sun conditions -- the Sun has brightened 30% over the past 4 billion years -- how was the Earth 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
Carbon Dioxide Cycle (CO2 a.k.a. Earth scycle) long-term thermostat
Carbon Dioxide Cycle (CO2 a.k.a. Earth scycle) long-term thermostat Rate dependent on temperature Temperature increases Temperature decreases more evaporation/ra infall less evaporation/ra infall less CO2 in atmosphere more CO2 in atmosphere less greenhouse effect more greenhouse effect Temperature decreases Temperature increases
Question: Let s recap! Which four unique features of Earth are important to life? 1) surface liquid water, oil, atmospheric Oxygen and 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
Question: Let s recap! Which four unique features of Earth are important to life? 1) surface liquid water, oil, atmospheric Oxygen and 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 activity changing our planet?
There are historical climate changes that occur naturally due to things like small cyclical changes in Earth s axis tilt or major volcanic releases of CO2. leads to ice ages (every 10,000 years or so)
Global Warming Global average temperature increased 0.8 C in past century
What is causing global warming?
The Greenhouse Effect greenhous e gases are: CO2 methane water vapor
The Greenhouse Effect greenhous e gases are: CO2 methane water vapor Note! Greenhouse Effect is crucial for life! But too much of a good thing can be bad... i.e. Venus
Proof? We see the greenhouse effect on other planets
CO2 levels today are higher than at any point in the past 400,000 years
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
Discussion Question: Imagine you are a scientist tasked 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
CO2 levels correlate with temperature
Discussion Questions
Discussion Questions Can you explain what this graph is showing?
Discussion Questions What could be causing the increase in CO2 levels over the past 50 years?
Discussion Questions Bonus points: Can you explain the detailed behavior of the data? (i.e. the red line)?
Alps, January 2004 Alps, June 2004
Effects of Global Warming?
Melting polar ice caps & Melting ice sheets Greenland white = year round ice sheet orange = melt region
FLOODING: sea level rise of 1 meter could occur within the century simply from heating of water
What makes a planet habitable?
Size Matters: Which cools faster? 2 1 3
Planetary Size Small Large
relative sizes Mercury Venus Earth Mars
Transit of Venus: June 5, 2012
Distance from Sun
Hot core enabled magnetic field
Magnetic field protects Earth from harmful solar particles and creates aurora borealis
To see original MOV file, click here
Now you are a scientist tasked with locating other Earth-like planets where human life could possibly exist. How would you do this?
Search for extrasolar planets Kepler Space Telescope
CO2 levels correlate with temperature