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

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.

4. 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.

6. The sounds

7. The witness

8. Photo of the smoke trail

9. Crater: diameter 14m

10. Carancas meteorites
Photo José Ishitsuka

12. Other meteorites found
22 gr
60 gr
20 gr

13. Chondrite
Achondrite
Iron

14. in the center and a thick olivine rim.
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

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

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

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

18. Meteor Crater Barringer, Arizona
Crater Manicouagan, Canada
100 km, 212 Myr
Crater Double Clearwater, Canada
kkm, 290 Myr
Meteor Crater Barringer, Arizona
1.2 km, yr

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

20. Recent records of impact craters
Year
Location of the crater
Diameter of largest crater
Number of craters or pits
Total mass of found meteorites
Meteorite type
1998
Kunya-Urgench, Turkmenistan
6 m
Single
1.1 tons
Chondrite H5
1990
Sterlitamak, Russia
10 m
0.3 tons
Iron IIIAB
1976
Jilin, China 4m
Multiple
4 tons
1947
Sikhote-Alin, Russia     
27 m
23 tons
Iron IIAB

21. Jilin, China (1976)
Penetration hole

22. Sterlitamak, Rusia (1990)

23. Sikhote-Alin (1947)

24. Sikhote-Alin strewn field

25. Carancas crater

27. Impact regimes

28. The size of the projectile

29. Impact Energy on the surface

30. Home experiment

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

33. Roof of a shed at ~75m from the crater impacted by ejecta

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

35. Speed of the ejected material

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

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

38. Quartz grains with shock metamorphism due to impact (Harris et al

39. 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

40. Infrasound and Seismic detections

41. 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)

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

43. 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

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

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

47. Elements compared with NEAs

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

49. 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

50. 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)

51. What else do we want to know?
Confirm the pressure and temperatures reached at the time of impact and the velocity of the impactor
What does happen with the original meteorite? Was it fragmented and totally dispersed during the impact?
How was it possible that a chondrite meteorite of just a few meters in size could get through the atmosphere without being completely disrupted?
In which conditions could this event happen again?

52. Research Team
G. Tancredi - Dpto. Astronomía, Fac. Ciencias, Iguá 4225, Montevideo, Uruguay,
J. Ishitsuka, D. Rosales, E. Vidal - Instituto Geofísico del Perú, Lima, Perú
P. Schultz, R. S. Harris - Dept. Geological Sciences, Brown University, Rhode Island, USA.
P. Brown - Dept. of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 Canada
D. Revelle - EES-2, Atmospheric, Climate and Environmental Dynamics Group – Meteorological Modeling Team, Los Alamos National Laboratory, P.O. Box 1663, MS D401, Los Alamos, NM USA
K. Antier, A. Le Pichon - Commissariat à l’Energie Atomique, Centre DAM - Ile de France, Département Analyse Surveillance Environnement, Bruyères-le-Châtel, Arpajon Cedex, France.
S. Benavente - Universidad Nacional del Altiplano, Puno, Perú
P. Miranda, G. Pereira - Planetario Max Schreier, Universidad Mayor de San Andrés, La Paz, Bolivia
M. E. Varela - Complejo Astronómico El Leoncito – CASLEO, San Juan, Argentina
F. Brandstätter - Naturhistorisches Museum, Vienna, Austria
L. Sánchez - Inst. Ciencias de la Tierra, Fac. Ciencias, Iguá 4225, Montevideo, Uruguay