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The first recorded impact crater on the Earth: Carancas, Peru

The first recorded impact crater on the Earth: Carancas, Peru. G. Tancredi and several colleagues from Peru and many other countries Dpto. Astronomía, Fac. Ciencias, Montevideo, Uruguay gonzalo@fisica.edu.uy. ¿What did happen?.

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The first recorded impact crater on the Earth: Carancas, Peru

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  1. The first recorded impact crater on the Earth: Carancas, Peru G. Tancredi and several colleagues from Peru and many other countries Dpto. Astronomía, Fac. Ciencias, Montevideo, Uruguay gonzalo@fisica.edu.uy

  2. ¿What did happen? • 15/9/2007 – ~ 11:45 LT (16:45 UT) a bright fireball was observed in the sky, leaving behind an smoke trail. Strong explosions lasting several seconds were heard in an area of several tens of km long. An explosion was observed as well as the formation of a thick cloud of dust like a mushroom cloud. • The shock wave produce the vibration of several houses and some animals were knocked down due to the shock wave. The roof of a shed was impacted by ejecta. • In the site where the explosion and the dust cloud was observed, the local people found a ~15m crater. The crater was half-fill by underground water. The water was bubbling and noxious fumes were coming out the water. • Several pieces of atypical material was collected from inside and outside the crater. • Several persons got sick.

  3. Preliminary considerations • A stony meteorite enter the upper atmosphere at velocities ~12-20 km/s. As a consequence of the friction with the air molecules, the body heats up and material from the surface is vaporized. The hot gas cloud that is formed around the body is observed as a fireball crossing the sky at high speed. The phenomena last just a few seconds. In its passage it leaves behind a smoke trail. Due to the supersonic speeds and possible fragmentations, the shock wave produces a sonic boom that last for several seconds. • Though the body is largely decelerated in the passage through the atmosphere, it retains an important fraction of its original spped and it impacts the ground producing a crater.

  4. The sounds

  5. The witness

  6. Photo of the smoke trail

  7. Crater: diameter 14m

  8. Carancas meteorites Photo José Ishitsuka

  9. Other meteorites found 22 gr 60 gr 20 gr

  10. Chondrite Achondrite Iron

  11. Photo 1: Transmitted light optical image. In the center a radiating pyroxene chondrule. Plane polarized light Photo2: Detail of the radiating pyroxene chondrule. Cross polarized light Photo3: Olivine rich object characterized by having a barred-olivine texture in the center and a thick olivine rim. Plane polarized light

  12. MINERALOGY COMPOSITION • Piroxene 1 40 % • Olivine 20 % • Feldespat 10 % • Piroxene 2 10 % • Opaque minerals accounting for 20 % of the mass, they inlcude: • Kamacite 15% • Troilite 5 % • Cromite traces • Cupper native traces Analysis from INGEMMET, Peru

  13. Clasification (M. E. Varela et al.) Ferrosilite in Ortopiroxene Fayalite in Olivine Ordinary Chondrite type H4/5

  14. Impact Crateres by comets and asteroids Crater Aristarco, Moon

  15. Crater Manicouagan, Canada 100 km, 212 Myr Crater Double Clearwater, Canada 32 6 22kkm, 290 Myr Meteor Crater Barringer, Arizona 1.2 km, 49.000 yr

  16. Tunguska, 1908 (photo taken by Kulik in 1928)

  17. Recent records of impact craters

  18. Penetration hole Jilin, China (1976)

  19. Sterlitamak, Rusia (1990)

  20. Sikhote-Alin (1947)

  21. Sikhote-Alin strewn field

  22. Carancas crater

  23. Impact regimes

  24. The size of the projectile

  25. Impact Energy on the surface

  26. Home experiment

  27. Ejecta at 300m in SW direction Big size ejecta at 100m in NE direction Location of ejecta in NE direction The ejected material

  28. Roof of a shed at ~75m from the craterimpacted by ejecta

  29. Distribution of ejected material (Rosales et al. 2008)

  30. Speed of the ejected material

  31. Shock Metamorphism of the target material and the projectile French (1998)

  32. Meteorites fragments embedded in the soil (Harris et al. 2008)

  33. Quartz grains with shock metamorphism due to impact (Harris et al. 2008)

  34. Conclusions about the petrology studies • The meteoritic mass penetrated deeply at a high speed while coupling its energy to the subsurface to produce surface spalls, inverted rim ejecta, injection of meteoritic debris between contrasting soil horizons, long crater rays, and excavation of horizons not exposed on the surface. • Regarding the level of shock metamorphism of the target material, we estimate Pressures > 10GPa • The impact velocity was > 3 km/s and possibly on the order of 4 to 6 km/s

  35. Infrasound and Seismic detections

  36. Infrasound detection (Brown et al. 2008) Infrasound station I08BO in La Paz, Bolivia (80 km from crater) Infrasound station I41PY in Asuncíon, Paraguay (1617 km from crater)

  37. Seismic detections (LePichon et al. 2008) First seismic detection of an extraterrestrial impact on Earth

  38. Estimate of the trajectory through the atmosphere • Facts to take into account • Backazimuth from infrasound station I08BO determined from the array of detectors • Arrival time in the seismic waves and of the air shoch waves at the seismic and infrasound stations • Witnesses that saw the fireball • Distribution of ejected material, concentration in the SW direction

  39. Orbital elements of the meteoroid • Impact time: 16h 40m 14s UT • Radiant: Az ~ 80-110° Alt ~ 45-60° • Pre-atmospheric velocity: 12-18 km/s

  40. Location of the radiants in equatorial coordinates relative to the Sun (Tancredi et al. 2008)  Radiants of NEAs  Sun  Anti-Sun

  41. Elements compared with NEAs

  42. Direct Entry Modeling Results: Example (D. Revelle et al.)

  43. Why is this event so relevant? • Fresh fall with many witnesses • An impact crater was formed • Impact at high latitude, less deceleration in the atmosphere • Ordinary chondrite meteorite that survives the passage through the atmosphere • Several records of infrasound and seismic data • Collection of material from the ground and the meteorite with shock metamorphism

  44. Preliminary Conclusions • Initial Mass of the meteoroid: 7 to 12 ton • Initial Diameter: 1.6 – 2 m • Initial Velocity: 12 – 17 km/s • Initial Energy: 0.12 – 0.41 kT TNT • Trayectory with Az: 80° - 110°, Alt: 45° - 60° • Impact Velocity on the ground: ~> 3 km/s • Mass of the impactor: 1 – 2.5 ton • Diameter: 0.8–1.1m ; Impact Energy: ~2–4 tons TNT • There is no indications of large remnants of the meteorite inside the crater (see Ishitsuka presentation)

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