ASTR-3040:Astrobiology

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ASTR-3040Astrobiology
The Origin Evolution of Life on Earth Chapter 6
Day 13
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Homework

• Due Tue. March 1
• Chapter 6
• 1, 4, 8, 13, 23, 28, 34, 35, 42, 46, 49, 52, 53,
  56
• Exam 1 Tuesday March 1
• Chapters 1 - 6

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Impacts Extinction
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Impacts Extinction

• Early dinosaurs 245 Myr ago.
• Evolved and ruled for 180 Myr
• Small mammals
• 65 Myrs ago, mass extinction Why?
• Also took out 99 of all life 75 of all
  species
• K-T boundary layer
• 1978 Luis Walter Alvarez
• Cretaceous-Tertiary boundary high in iridium.

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More Evidence

• Besides Iridium
• 1. high metal abundances Os, Au, Pl
• 2. Shocked Quartz grains (hig Temp, Press)?
• 3. Spherical rock droplets
• 4. Soot (global fires)?

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Oh yeah, a Crater!
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Other Mass Extinctions

• About every 65-75 Myr (5 major events)?
• Other than impact - nuclear winter effect

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Other Ideas

• Active volcanic activity climate change
• UV increase mutation rates
• Supernovae cosmic rays
• GRBs destroy ozone layer
• What have we learned?
• It could happen again.

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Tunguska 1908 40m airburst
SL9 1994 Jupiter
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Human Evolution

• How did we evolve?

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Humankind

• Sahelanthropus tchadensis
• Are we still evolving?