2. Is there anyone else out there?

3. The Drake Equation Number of stars # stars with planet # planets that could support life # number that evolve life # fraction of life that becomes smart # fraction that can/want to communicate # how long they last before blowing up Number of stars # stars with planet # planets that could support life # number that evolve life # fraction of life that becomes smart # fraction that can/want to communicate # how long they last before blowing up

4. What is geophysics? The use of physics to study the Earth and planets

5. Geodynamic simulations Solving the whole world: mantle convection

6. Geodynamic simulations mantle convection: hot air rises? So does hot mantle. And when it does, it does this: mantle convection: hot air rises? So does hot mantle. And when it does, it does this: The continents drift! This is called plate tectonics. The continents drift! This is called plate tectonics.

7. Why is the mantle important for Earth? Water & CO2 both come out of volcanoes into the atmosphere. Both are recycled back into the mantle by plate tectonics (oceans recycled through the mantle over 10 times through Earth’s history!) On Earth, plate tectonics controls the atmosphere and oceans (and so it also affects life…). -> The plate tectonic cycle helps control global warming Water & CO2 both come out of volcanoes into the atmosphere. Both are recycled back into the mantle by plate tectonics (oceans recycled through the mantle over 10 times through Earth’s history!) On Earth, plate tectonics controls the atmosphere and oceans (and so it also affects life…). -> The plate tectonic cycle helps control global warming

8. Spot the difference

9. Venus ca. 1930

10. Venus ca. 1930

15. Magellan mission in early 90’s: 1. No plate tectonics 2. No continents 3. The surface of Venus is all about the same age Magellan mission in early 90’s: 1. No plate tectonics 2. No continents 3. The surface of Venus is all about the same age

16. Why wouldn’t Venus have plate tectonics like Earth? Sun Theory: No water, no plate tectonics Earth Venus Mars Water

17. So Earth is lucky cause its got little CO2. But where did all the CO2 go??? So Earth is lucky cause its got little CO2. But where did all the CO2 go???

18. So life protects the Earth from runaway greenhouse and boiling oceans… But water and oceans are needed for life…? So life protects the Earth from runaway greenhouse and boiling oceans… But water and oceans are needed for life…? Earth is 4.5 billion years old We see life back to nearly 4 billion years, it could be older Earth is 4.5 billion years old We see life back to nearly 4 billion years, it could be older

19. So life protects the Earth from runaway greenhouse and boiling oceans… But water and oceans are needed for life…? So life protects the Earth from runaway greenhouse and boiling oceans… But water and oceans are needed for life…? Earth is 4.5 billion years old We see life back to nearly 4 billion years, it could be older Earth is 4.5 billion years old We see life back to nearly 4 billion years, it could be older Ancient zircon grains: earliest life on Earth Tough zircon grains in younger rocks Zircon dates are >4.0Ga, even as old as 4.4Ga. This is just after the world formed. Oldest exposed rocks (Canada) are ~4.0Ga. These zircons are from worlds oldest continents. Their chemistry indicates liquid water too. They have diamonds in them... and the diamond chemistry indicates the presence of life! (Maybe)

20. The big fluke Made the moon Evaporated Earth’s atmosphere Later atmosphere from volcanoes was thin and cool so oceans could form, and life could evolve Venus never lost its big blanket so it was always to hot for oceans It even has a “fossil atmosphere” (the fossil is Argon. Earth’s got blasted into space).

21. So no life on Venus? Ever? Well, not so quick…. 2002: El Paso, Texas -> detected strange chemicals in the clouds H2S & SO2 together, carbonyl sulphide, and no CO So what? These are not naturally found together, only when life-forms are producing them. 2002: El Paso, Texas -> detected strange chemicals in the clouds H2S & SO2 together, carbonyl sulphide, and no CO So what? These are not naturally found together, only when life-forms are producing them. Bacteria in clouds? Why not, they live there on Earth. Bacteria in clouds? Why not, they live there on Earth.

22. Life can turn up in the strangest places. Earth might be rare, but maybe that doesn’t matter. Also check out: http://www.cosmosmagazine.com/node/1658 Also check out: http://www.cosmosmagazine.com/node/1658