Terrestrial World Surfaces

Transcription

1 1 Terrestrial World Surfaces Solid rocky surfaces shaped (to varying degrees) by: Impact cratering Volcanism Tectonics (gross movement of surface by interior forces) Erosion (by impacts or by weather)

2 2 Impact Cratering Small bodies in the Solar System can strike larger bodies at tremendous speed (many kilometers per second). The tremendous energy of motion gets converted into an explosion at the point of contact. Large impactors don't gouge they detonate. Large craters are round independent of the angle of impact. Mars Moon Iapetus (Saturn)

3 3 Impact Cratering Small bodies in the Solar System can strike larger bodies at tremendous speed (many kilometers per second). The tremendous energy of motion gets converted into an explosion at the point of contact. Large impactors don't gouge they detonate. Large craters are round independent of the angle of impact.

4 4 Impact Cratering Upon impact the surface temporarily behaves like a liquid. Cratering can be reminiscent of tossing a rock in a pond. Craters can have central mountain peaks. Large impacts form multi-ring basins

5 5 Impact Cratering Upon impact the surface temporarily behaves like a liquid. Cratering can be reminiscent of tossing a rock in a pond. Craters can have central mountain peaks. Large impacts form multi-ring basins

6 6 Impact Cratering Upon impact the surface temporarily behaves like a liquid. Cratering can be reminiscent of tossing a rock in a pond. Craters can have central mountain peaks. Large impacts form multi-ring basins

7 7 Impact Cratering Upon impact the surface temporarily behaves like a liquid. Cratering can be reminiscent of tossing a rock in a pond. Craters can have central mountain peaks. Large impacts form multi-ring basins

8 8 Ejecta Blankets Impacts splash out material that blankets surrounding terrain.

9 9 Ejecta Blankets Impacts splash out material that blankets surrounding terrain.

10 10 Terrestrial World Surfaces For the Moon... Solid rocky surfaces shaped (to varying degrees) by: Impact cratering Volcanism (lava floods within Maria) Tectonics (gross movement of surface by interior forces) Erosion (via impact grinding, not atmospheric)

11 11 Geological Activity vs. Planetary Size It's no coincidence that the smallest worlds above are the ones that are heavily cratered. The larger a world is the more readily it retains its internal heat. A pea cools off much more quickly than a potato Earth and Venus are still hot in the interior and molten material can reach and re-surface the surface.

12 12 Geological Activity vs. Planetary Size Planets start out hot and generate heat internally through radioactive decay. The larger a world is the more readily it retains its internal heat. A pea cools off much more quickly than a potato Earth and Venus are still hot in the interior and molten material can reach and re-surface the surface.

13 Two Extremes: Rampant Volcanism vs. Early Geological Death 13

14 14 Geological Activity vs. Planetary Size It's no coincidence that the smallest worlds above are the ones that are heavily cratered. The larger a world is the more readily it retains its internal heat. A pea cools off much more quickly than a potato Earth and Venus are still hot in the interior and molten material can reach and re-surface the surface.

15 Geologic Activity on Earth and Venus 15

16 16 Geologic Activity on Earth and Venus

17 17 Geological Activity vs. Planetary Size It's no coincidence that the smallest worlds above are the ones that are heavily cratered. The larger a world is the more readily it retains its internal heat. A pea cools off much more quickly than a potato Earth and Venus are still hot in the interior and molten material can reach and re-surface the surface.

18 18 Mercury Being small, it ended geological activity relatively early and is a heavily cratered world.

19 19 Mercury Being small, it ended geological activity relatively early and is a heavily cratered world.

20 20 Mercury Possibly not as heavily cratered as the lunar highlands because it took longer to cool.

21 21 Earth Impacts and Why You Might Care Impact craters are ubiquitous throughout the Solar System Saturn's icy moon Rhea Earth's Moon

22 22 Earth Impacts and Why You Might Care Impact craters are ubiquitous throughout the Solar System

23 23 Earth Impacts and Why You Might Care Bombardment is a natural consequence of the cleanup of the Solar System following the initial accretion of the planets.

24 24 Earth Impacts and Why You Might Care What was a heavy bombardment has tapered off to a light peppering

25 25 Earth Impacts and Why You Might Care The Solar System is still full of potential large impactors.

26 26 no, no, NO, NO, NO!!!!!!!

27 27 Earth Impacts and Why You Might Care The Earth has been impacted as much as the Moon (actually more because of its stronger gravity) The (thin) atmosphere does little to protect against large impactors.

28 28 Earth Impacts and Why You Might Care The Earth has been impacted as much as the Moon (actually more because of its stronger gravity) The (thin) atmosphere does little to protect against large impactors.

29 29 Earth Impacts and Why You Might Care Erosion and resurfacing have erased all but the most recent impact scars.

30 30 The Arrival Rate of Impactors vs. Size A beachball-sized object strikes Earth daily. Objects 10 kilometers in size strike once every 100 million years. Asteroid collisions produce lots of small fragments and a few big ones.

31 31 The Arrival Rate of Impactors vs. Size A beachball-sized object strikes Earth daily. Objects 10 kilometers in size strike once every 100 million years. Objects smaller than a few tens of meters in size don't reach the ground intact.

32 32 The Delivered Energy Can be Huge Traveling at speeds up to 10's of kilometers per second, the kinetic energy of these objects is substantial.

33 33

34 34 Large Impacts and Mass Extinctions The fossil record contains notable episodes where many (if not most) of the species on Earth disappeared.

35 35 Large Impacts and Mass Extinctions The frequency of these events is consistent with the arrival rate of impactors 10 kilometers in size (roughly every 100 million years). Such an impactor triggers global fires and contaminates the stratosphere with enough dust to blot out the Sun for years. The food chain collapses and many species die out.

36 36 Large Impacts and Mass Extinctions The frequency of these events is consistent with the arrival rate of impactors 10 kilometers in size. Evidence that such events happen includes the presence of excess iridium in geologic layers that mark mass extinctions. Iridium is rare on the Earth's surface but common in meteorites. A worldwide iridium rich layer is coincident with the demise of the dinosaurs The Cretaceous-Tertiary (KT) boundary

37 37

38 38 The Demise of the Dinosaurs If dinosaurs were wiped out by an impact 65 million years ago there had better be better evidence than some extra iridium in the ground... and there is.

39 39 The Demise of the Dinosaurs If dinosaurs were wiped out by an impact 65 million years ago there had better be better evidence than some extra iridium in the ground... and there is... a buried impact crater nearly 100 miles in diameter in the Yucatan dating back 65 million years.

40 40 The Demise of the Dinosaurs If dinosaurs were wiped out by an impact 65 million years ago there had better be better evidence than some extra iridium in the ground... and there is... melted glass beads formed in the impact are spread across North America and embedded in the KT boundary.

41 41 The Demise of the Dinosaurs

42 Well, it's a good thing that can't happen to us... 42

43 43 Assessing the Odds Rank the items below (which include three different impact hazards) from least likely to most likely.

44 44 The Modern Impact Hazard 65 million years is not all that long ago. We run the same risks as the Dinosaurs. A mass extinction level impact is improbable, but smaller impacts that might have devastating consequences happen much more frequently.

45 45 The Modern Impact Hazard The last major event with significant consequences (destruction of a city-sized area) occurred only a century ago. Tunguska, Siberia in 1908

46 46 The Modern Impact Hazard Every few 10's of thousands of years an object a few hundred meters in size arrives depositing the energy of a few hundred thermonuclear explosions. Such an impact in an ocean (70% of the Earth's surface) would set off devastating tidal waves that would destroy coastal cities.

47 47 Shouldn't We Do Something about It? We live during the first time in Earth history where we can modify the odds in our favor. Seek out potentially hazardous asteroids. Find the one(s) that are on a direct collision course Nudge them so that they miss the Earth.

48 48 Shouldn't We Do Something about It? We live during the first time in Earth history where we can modify the odds in our favor. Seek out potentially hazardous asteroids. Find the one(s) that are on a direct collision course Nudge them so that they miss the Earth.

49 49 Shouldn't We Do Something about It? We live during the first time in Earth history where we can modify the odds in our favor. Seek out potentially hazardous asteroids. Find the one(s) that are on a direct collision course Nudge them so that they miss the Earth.

50 50 Shouldn't We Do Something about It? We live during the first time in Earth history where we can modify the odds in our favor. Seek out potentially hazardous asteroids. Find the one(s) that are on a direct collision course Nudge them so that they miss the Earth.

51 51 A Success of the System: 2008 TC3 19 hours before Earth impact the Catalina Sky Survey picked up a small asteroid, the size of a pickup truck, headed for the African Nubian desert.

52 52 A Success of the System: 2008 TC3 The observation enabled the prediction of the impact location.

53 53 A Success of the System: 2008 TC3 The observation enabled the prediction of the impact location... and recovery of samples

54 54 A Success of the System: 2008 TC3 The observation enabled the prediction of the impact location... and recovery of samples

55 55 Shouldn't We Do Something about It? We live during the first time in Earth history where we can modify the odds in our favor. Seek out potentially hazardous asteroids. Find the one(s) that are on a direct collision course Nudge them so that they miss the Earth. Asteroid Apophis 320 meters in diameter (Friday) April 13, 2029

56 56 Shouldn't We Do Something about It? At what cost? An investment of a few hundred million dollars is required to find the threats. Congressional mandate: Find all Potentially Hazardous Asteroids >140 meters by

57 57 Things that Cost around 200 Million Dollars Production cost of a (scientifically horrendous) movie about the asteroid impact hazard.

58 58 Your Favorite Baseball Player Alex Rodriguez, $275,000,000 ( ) Alex Rodriguez, $252,000,000 ( ) Derek Jeter, $189,000,000 ( ) Mark Teixeira, $180,000,000 ( ) CC Sabathia, $161,000,000 ( ) Manny Ramirez, $160,000,000 ( ) Miguel Cabrera, $152,300,000 ( ) Todd Helton, $141,500,000 ( ) Johan Santana, $137,500,000 ( ) Alfonso Soriano, $136,000,000 ( )

59 59 1/10th of an Aircraft Carrier

60 60 1/3 of a Space Shuttle Launch

61 61 The JPJ -or- The South Lawn 131 and 105 million respectively.

62 62 Shouldn't We Do Something about It? We live during the first time in Earth history where we can modify the odds in our favor. Seek out potentially hazardous asteroids. Find the one(s) that are on a direct collision course Nudge them so that they miss the Earth. Nuclear explosion nearby Paint one side white! Gravity tractor

63 63 Shouldn't We Do Something about It? We live during the first time in Earth history where we can modify the odds in our favor. Seek out potentially hazardous asteroids. Find the one(s) that are on a direct collision course Nudge them so that they miss the Earth. Nuclear explosion nearby Paint one side white! Gravity tractor