Transcript Is there anyone else out there?

Is there anyone else out there?
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
What is geophysics?
The use of physics to study the Earth and planets
Geodynamic simulations
Solving the whole world: mantle convection
Geodynamic simulations
mantle convection: hot air rises?
So does hot mantle.
And when it does, it does this:
The continents drift!
This is called plate tectonics.
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
Spot the difference
Venus
ca. 1930
Venus ca. 1930
Venus ca. 1930
Magellan mission in early 90’s:
1. No plate tectonics
2. No continents
3. The surface of Venus is all
about the same age
Why wouldn’t Venus have
plate tectonics like Earth?
Theory: No water, no plate tectonics
Sun
Venus
Water
Earth
Mars
So Earth is lucky cause its
got little CO2.
But where did all the CO2
go???
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
Ancient zircon grains: earliest
life protects
on Earth the Earth
So life
from runaway greenhouse
Tough zircon grains in younger rocks
and boiling oceans…
Zircon dates are >4.0Ga, even as old as
4.4Ga. This is just after the worldBut water and oceans are
formed.
needed for life…?
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)
Earth is 4.5 billion years old
We see life back to nearly 4 billion
years, it could be older
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).
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.
Bacteria in clouds?
Why not, they live there on Earth.
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