Presentation on theme: "The first recorded impact crater on the Earth: Carancas, Peru"— Presentation transcript:
1 The first recorded impact crater on the Earth: Carancas, Peru G. Tancredi and several colleagues from Peruand many other countriesDpto. 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.
14 in the center and a thick olivine rim. Photo 1: Transmitted light optical image. In the center a radiating pyroxene chondrule. Plane polarized lightPhoto2: Detail of the radiating pyroxene chondrule. Cross polarized lightPhoto3: Olivine rich object characterized by having a barred-olivine texturein 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 tracesCupper native tracesAnalysis from INGEMMET, Peru
16 Clasification (M. E. Varela et al.) Ferrosilite in OrtopiroxeneFayalite in OlivineOrdinary Chondrite type H4/5
17 Impact Crateres by comets and asteroids Crater Aristarco, Moon
18 Meteor Crater Barringer, Arizona Crater Manicouagan, Canada100 km, 212 MyrCrater Double Clearwater, Canadakkm, 290 MyrMeteor Crater Barringer, Arizona1.2 km, yr
19 (photo taken by Kulik in 1928) Tunguska, 1908(photo taken by Kulik in 1928)
20 Recent records of impact craters YearLocation of the craterDiameter of largest craterNumber of craters or pitsTotal mass of found meteoritesMeteorite type1998Kunya-Urgench, Turkmenistan6 mSingle1.1 tonsChondrite H51990Sterlitamak, Russia10 m0.3 tonsIron IIIAB1976Jilin, China4mMultiple4 tons1947Sikhote-Alin, Russia 27 m23 tonsIron IIAB
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 estimatePressures > 10GPaThe impact velocity was > 3 km/s and possibly on the order of 4 to 6 km/s
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 accountBackazimuth from infrasound station I08BO determined from the array of detectorsArrival time in the seismic waves and of the air shoch waves at the seismic and infrasound stationsWitnesses that saw the fireballDistribution of ejected material, concentration in the SW direction
48 Direct EntryModelingResults:Example(D. Revelle et al.)
49 Why is this event so relevant? Fresh fall with many witnessesAn impact crater was formedImpact at high latitude, less deceleration in the atmosphereOrdinary chondrite meteorite that survives the passage through the atmosphereSeveral records of infrasound and seismic dataCollection of material from the ground and the meteorite with shock metamorphism
50 Preliminary Conclusions Initial Mass of the meteoroid: 7 to 12 tonInitial Diameter: 1.6 – 2 mInitial Velocity: 12 – 17 km/sInitial Energy: 0.12 – 0.41 kT TNTTrayectory with Az: 80° - 110°, Alt: 45° - 60°Impact Velocity on the ground: ~> 3 km/sMass of the impactor: 1 – 2.5 tonDiameter: 0.8–1.1m ; Impact Energy: ~2–4 tons TNTThere 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 impactorWhat 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 TeamG. Tancredi - Dpto. Astronomía, Fac. Ciencias, Iguá 4225, Montevideo, Uruguay,J. Ishitsuka, D. Rosales, E. Vidal - Instituto Geofísico del Perú, Lima, PerúP. 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 CanadaD. 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 USAK. 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, PerúP. Miranda, G. Pereira - Planetario Max Schreier, Universidad Mayor de San Andrés, La Paz, BoliviaM. E. Varela - Complejo Astronómico El Leoncito – CASLEO, San Juan, ArgentinaF. Brandstätter - Naturhistorisches Museum, Vienna, AustriaL. Sánchez - Inst. Ciencias de la Tierra, Fac. Ciencias, Iguá 4225, Montevideo, Uruguay