1. Meteor(ites) and Potentially Hazardous Objects Kuliah AS3141 Benda Kecil dalam Tata Surya Budi Dermawan Prodi Astronomi 2006/2007

2. 2 Penetrating the Atmosphere from meteoroid to meteorite

3. 3 Moving Through the Atmosphere

4. 4 Meteor Shower

5. 5 Famous Meteor Showers

6. 6 Meteoroids Swarm & Size When a comet approaches perihelion, sublimation of the nucleus liberates particles trapped in ice of which it is formed  a swarm When the Earth encounters such a swarm it intercepts the particles, the more the closer it passes to the orbit of the comet itself Size radius: a few tenth mm – a few cm

7. 7 Meteorite Types Types (1) Types (2)

8. 8 Meteorites Isotopic Anomalies (1) Oxygen 16 O: 17 O: 18 O  0.9527:0.0071:0.0401 (SMOW: Standard Mean Ocean Water) three-isotope plot: slope 0.5 (terrestrial), slope ~1 chondrites Magnesium 24 Mg: 25 Mg: 26 Mg  0.790:0.100:0.110 three-isotope plot: slope 0.5 Excess in 26 Mg  amount of 27 Al Neon 20 Ne: 21 Ne: 22 Ne  0. 9051:0.0027:0.0922 three-isotope plot: triangle region there is high enriched 22 Ne (neon-E)

9. 9 Meteorites Isotopic Anomalies (2) Silicon Carbide Grains 28 Si: 29 Si: 30 Si  0.9223:0.0467:0.0310 SiC three-isotope plot: slope 1.3 Some SiC: ‘heavy carbon’, ‘light nitrogen’ Deuterium 1 H (H): 2 H (D)  various ratios

10. 10 Hazardous Objects Comets Asteroids (NEAs)

11. 11 NEAs

12. 12 Impact Craters Fireballs or Bolides Locally Devastating Impacts Globally Catastrophic Impacts Impact Types

13. 13 Explosion

14. 14 A Spectacular Moment Grand Teton National Park (Wyoming) 1972 Aug 10 Fireball

15. 15 Tunguska-Siberia Explosion 1908 Locally Devastating Impact + Airburst

16. 16 The Great Chicxulub Impact  65 Myr Ago Globally Catastrophic Impact End of Cretaceous period

17. 17 The Bedout Impact  250 Myr Ago Becker et al. 2004 Offshore of north-western Australia Globally Catastrophic Impact End of Permian period

18. 18 Impact Tsunami: Asteroid Eltanin

19. 19 Impact Tsunami: Asteroid 1950DA (1) Ward & Asphaug 2003

20. 20 Impact Tsunami: Asteroid 1950DA (2)

21. 21 … and March 2004 asteroid size:  30-m  0.1 Earth  Moon distance (!)

22. 22 Impact Estimates  26 – 31 Myr (Alvarez et al. 1980; Rampino & Haggerty 1994) Morrison et al. 1994 Periodicity of extinction events? Hiroshima bomb Tunguska explosion Chicxulub impact

23. 23 Destruction & Fatalities

24. 24 Asteroids Threatening Our Earth Types (based on the close-approach distance) Higher-risk   4 Lunar Distance (LD) Dangerous   1 LD Data  3 Aug 2006 Potentially Hazardous Asteroids (PHAs,  20 LD) Near Earth Object Program of NASA Minor Planet Center Until Year 2100

25. 25 Higher-risk Hazards  Three Dangerous Hazards

26. 26 Higher-risk & Dangerous Hazards

27. 27 Hazard Impact Risk Sizes of the three Dangerous Hazards:  0.04 –  0.9 km Locally Devastating Impacts Globally Catastrophic Impacts

28. 28 Orbit Diagram Data 2006/8/3  27 higher-risk 3 dangerous

29. 29 Preventing Impacts Survey and discovery of NEOs Accurate orbit determination Composition and gross properties Coordination of astronomical observations Studies of impacts and environmental and social effects Mitigation possibilities

30. 30 Some Mitigation Scenarios (1) Mitigation Procedures: - Orbit Deflection - Object Dispersion (e.g. Ahrens & Harris 1992)

31. 31 Some Mitigation Scenarios (2)

32. 32 Collaboration Work International: Spaceguard Survey Network Find 90% of  1 km asteroids by 2008 Japan Spaceguard Association e.g. Bisei Spaceguard Center (Okayama) Indonesia: (?)

33. 33 PHOs Summary Asteroid impacts: rare example of hazard. Low probability but high consequences. Monitoring observations will significantly improve their encounter distances. Aware of the efforts supported and operated by international basis for lowering the impact risks.

34. 34 The End NASA

35. 35 Quebec ‘Twin’ Craters Terrestrial Impact Craters

36. 36 Sizes of Asteroids Bowell et al. 1989: p v = 0.21  0.05 (Silicate) 0.06  0.02 (Carbonaceous) [Dermawan 2004]

37. 37 Impact Interval

38. 38 Average Annual Risk of Death in parts per Million 300 Accidents (not motor vehicle) 200 Homicide & suicide 160 Motor vehicle accidents 10 Fire 5 Electrocution 1 Airplane accidents 0.5 Total Impacts (global threshold) 0.3 Storms and floods (declining) 0.1 Local/Regional Impacts 0.1 Earthquakes (poor statistics) 0.01 Tunguska-like Impacts < 0.01 Nuclear accidents (design goals)

39. 39 Average Annual Risk of Death in parts per Million 1 Total Impact Risk 0.1 Risk from Local/Regional Impacts (< 2 km) 0.01 Risk from Tunguska-like impacts (< 300 m) 50 Bangladesh (primarily floods) 25 China (primarily floods & earthquakes) 20 Turkey/Iran/Turkmenistan (primarily earthquakes) 15 Japan (primarily earthquakes) 10 Caribbean & Central America (storms, earthquakes, volcanoes) < 1 Europe < 0.1 USA/Canada

40. 40 Geologic Timescale