Life on Earth

1. Life on Earth

2. What We Learn From Other Planetary Systems • Protoplanetary Disks • Accretion of Planets • Expulsion and Migration of Planets • About 1000 extrasolar planets known • Our Solar System may be unusual?

3. Protoplanetary Disks in Orion

4. The Galactic Habitable Zone? • Center: Too Violent, Stars too massive and short-lived • Fringes: Not enough material to make suitable planets • Middle: Stable but frequent star formation, expulsion of new material

5. Do We Need Jupiter for Life? • Close-in Jupiter: other planets not possible • Jupiter in eccentric orbit: other planets won’t have stable orbits • Distant Jupiter in circular orbit is a stabilizing influence • Jupiter sweeps up a lot of potential impactors

6. Do We Need the Moon for Life? • Moon’s gravity causes the earth’s axis to precess • Mars’ axis tilt can be up to 60 degrees • Moon totally dominates effects of Sun and other planets, keeps earth’s axis tilt within reasonable limits

7. “Of course, long before you mature, most of you will be eaten.”

8. “The picture’s pretty bleak, gentlemen. The earth’s climate is changing, the mammals are taking over, and we all have brains the size of a walnut.”

9. “Now this end is called the thagomizer, after the late Thag Simmons.”

10. “Evolution’s been good to you, Sid.”

11. Prebiotic Evolution • The basic molecules of organic chemistry are easily made • The first self-replicating molecule was almost certainly not DNA • DNA assembles from simpler materials all the time

12. Plants and Animals • CO2 + H2O + Energy = Sugars, Starches, etc. + O2 (toxic waste) • O2 is actually toxic (even to us!) • Idea: Take the sugars and starches (from somebody else) combine it with the waste O2, and get energy

13. Amazing Events in Life History • Sex - Who Needs It? • We are a team - Mitochondria • The Great Freeze 900-600 m.y. ago • What survived and how? • Mass Extinctions • Dinosaurs = 4th worst • Permian extinction (220 m.y. ago) took out 90% of all species

14. Classification of Dogs and Humans • Kingdom Animalia • Phylum Chordata • Class Mammalia • Order Carnivora (Dogs) Primates (Humans) • Family Canidae Hominidae • Genus Canis Homo • Species familiaris sapiens

15. Strigiphilus garylarsoni “Actually, I considered this an extreme honor. Besides, I knew no one was going to write and ask to name a new species of swan after me. You have to grab these opportunities when they come along.”

16. The Five Kingdom System • Animals • Plants • Protista (one-celled organisms) • Fungi • Bacteria* • Ediacaran Fossils? (ca. 700 m.y. ago)

17. What’s Bigger Than a Kingdom? • Bacteria differ from all other kingdoms in lacking a cell nucleus • We need a bigger box • Superkingdoms or Domains • Monera (Bacteria) • Archaea • Eukarya (have cell nucleus) • Need electron microscopes and molecular biology to see differences

18. Mass Extinctions

19. Impacts on Earth

20. Recent Impact – Meteor Crater

21. Manicouagan, Quebec

22. Sudbury, An Ancient Impact Site

23. A Shatter Cone

24. Fallback Breccia

25. Bessel: A Simple Crater

26. Ejecta around Timocharis

27. Tycho: A Central-Peak Crater

28. How Central Peaks Form

29. Upheaval Dome, Utah

30. Schrodinger: A Peak-Ring Crater

31. Mare Orientale A Multiple-Ring Impact Basin

32. Impacts and Extinctions • The problem isn’t killing things, it’s that anything survives. • Immediate: Fireball, Blast, Ejecta • Hours: Tsunamis, Incoming ejecta • Days: Wildfires, Dust Cloud, Sulfur Aerosols • Months: Darkness, Death of plants and animals, acid rain • Years: CO2 or Methane pulse?

33. Were The Dinosaurs Failures? Dinosaurs: 150,000,000 years Recorded History: 5000 years • For every year of recorded history, the dinosaurs had 30,000 years • For every day of recorded history, the dinosaurs had 82 years • For every minute of recorded history, the dinosaurs had three weeks