ET Life #10. Neat Scale of the Universe flash animation Today: Finish up Impacts Earth Geologic Activity & Life

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Cameron Bishop
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1 ET Life #10 Neat Scale of the Universe flash animation Today: Finish up Impacts Earth Geologic Activity & Life

2 Apophis

3 Energy At 390 m, impacting at 13 km/s 2e18 Joules 510 megatons Meteor Crater (4000 ft crater): 3-10 megatons Krakatoa eruption (1883): 200 megatons Largest H-bomb ever: 50 megatons Chicxulub (10 km impactor) 100,000,000 megatons

4 Energy of an impact Kinetic Energy = ½ M V^2 M ~ R^3 So if you double the impactor Radius, you multiply the impact energy by 8 2^3 = a factor of 8

6 Chicxulub

7 K-T Layer

8 No, Dinosaurs are not Extinct Domain Kingdom Phylum Class Order Family Genus Species Super Order

9 Ways to avoid impacts? The gravity tractor? Bombs?

12 500,000

13 Does this sound right? There are 7 billion people alive today

14 How do they get that number? Probability of dying from an = asteroid impact ( Probability of a small asteroid hitting the earth/year Probability of a medium asteroid hitting the earth/year Probability of a large asteroid hitting the earth/year x x x Expected number of people who will die per impact Expected number of people who will die per impact Expected number of people who will die per impact Total Number of People ) + + x human lifetime

16 How do they get that number? Extraordinarily Small (hasn't happened as far as we know) Much larger than 1 Probability of dying from an = asteroid impact ( Probability of a small asteroid hitting the earth/year Probability of a medium asteroid hitting the earth/year x x Expected number of people who will die per impact Expected number of people who will die per impact + + Billions of people Extremely Extremely Small per year... but has Probability of a large asteroid hitting happened many times in the history of the earth the earth/year x Expected number of people who will die per impact Total Number of People ) x human lifetime

17 10 Most Deadly Volcanoes Mt. Tambora, Indonesia Mt. Vesuvius, Italy April 10-15, 1816 April 24, AD 79 Death Toll: 92,000 Death Toll: 10,000+ Mt. Pelee, West Indies The Laki Volcanic System, Iceland April 25 - May 8, 1902 June 8, February 1784 Death Toll: 40,000 Death Toll: 9350 Mt. Krakatoa, Indonesia Mt. Vesuvius, Italy August 26-28, 1883 December 1631 Death Toll: 36,000 Death Toll: 6,000 Nevado del Ruiz, Columbia Mt. Kelut, Indonesia November 13, 1985 May 19, 1919 Death Toll: 23,000 Death Toll: 5,110 Mt. Unzen, Japan Mt. Galunggung, Java, Indonesia Death Toll: 12,000-15,000 Death Toll: 4,011

18 Sources of Heat Heat of accretion (past) Potential and kinetic energy of colliding planetesimals was converted to heat. Heat of differentiation (past & today) Gravitational potential energy was converted to heat through friction as Earth differentiated. Radioactive decay (past & today) Decay from parent to daughter isotopes generates heat: 238U 206Pb 40K 40Ar Important in the past: 26Al 26Mg, 235U 207Pb

19 How much Heat did each of the terrestrial planets start out with? Radioactive Decay ~M~R 3 Accretion ~ M2 ~ R6 Differentiation ~ M2 ~ R6

20 How fast can the planets cool? Radiate from the surface ~ R2 If your surface is hotter you can cool faster ~ T4 (Wien's Law) Internal Energy ~ R6 Cooling rate ~ R2 Cooling time =Energy/Rate ~ R4

21 Geologically Dead or Alive?

22 Does a planet need to be geologically active to support life? Volcanism & Plate Tectonics Form the first atmosphere (W) Long term regulation of the climate (F) Magnetic Field Navigation for Animals Protects the atmosphere from Solar Wind (especially the ozone layer)

23 Other planets and Geologic Activity Volcanism Plate Tectonics Magnetic Field Mercury Some in past No Yes Venus A lot in past No No Earth Yes Yes Yes Mars A lot in past No Past

25 Internal structure from Earthquakes

26 Heat Transport Convection bulk flows transport energy Conduction molecules bump into their neighbors and transport energy Radiation Photons carry energy through space

27 Convection starts when conduction and radiation don't transport heat fast enough* *and hotter stuff is able to float away from the heat source

28 Convection

29 Which will be hotter? Heat Source B water A Heat Source

30 The Earth is Convecting Very Slooowly Is the Mantle Solid or Liquid?

32 Convection moving the Crust

Importance of Solar System Objects discussed thus far. Interiors of Terrestrial Planets. The Terrestrial Planets

Importance of Solar System Objects discussed thus far Interiors of Terrestrial Planets Chapter 9 Sun: Major source of heat for the surfaces of planets Asteroids: Provide possible insight to the composition