Analysis of a crater‐forming meteorite impact in Peru

Abstract

[1] The fireball producing a crater-forming meteorite fall near Carancas, Peru, on 15 September 2007 has been analyzed using eyewitness, seismic, and infrasound records. The meteorite impact, which produced a crater of 13.5 m diameter, is found to have released of order 10 10 J of energy, equivalent to $2-3 tons of TNT high explosives based on infrasonic measurements. Our best fit trajectory solution places the fireball radiant at an azimuth of 82°relative to the crater, with an entry angle from the horizontal of 63°. From entry modeling and infrasonic energetics constraints, we find an initial energy for the fireball to be in the 0.06-0.32 kton TNT equivalent. The initial velocity for the meteoroid is restricted to be below 17 km/s from orbit considerations alone, while modeling suggests an even lower best fit velocity close to 12 km/s. The initial mass of the meteoroid is in the range of 3-9 tons. At impact, modeling suggests a final end mass of order a few metric tons and impact velocity in the 1.5-4 km/s range. We suggest that the formation of such a substantial crater from a chondritic mass was the result of the unusually high strength (and corresponding low degree of fragmentation in the atmosphere) of the meteoritic body. Additionally, the high altitude of the impact site (3800 m.a.s.l) resulted in an almost one order of magnitude higher impact speed than would have been the case for the same body impacting close to sea level.

The Carancas meteorite impact crater, Peru: Geologic surveying and modeling of crater formation and atmospheric passage

“…The impact velocity was estimated in a number of recent studies and shows a remarkable range: 4-6 kms −1 ), >3 kms -1 (Tancredi et al 2008b), 3 kms −1 (Tancredi et al 2008a), 2-4 kms −1 (BoroviËka and Spurný 2008), 1.5-4 kms −1 (Brown et al 2008); >1.5 kms −1 (Le Pichon et al 2008), and 0.2-0.3 kms −1 (Kenkmann et al 2008a(Kenkmann et al , 2008b.…”

“…The entry of the Carancas meteoroid produced infrasound waves that were recorded by two infrasound arrays of the International Monitoring System for the enforcement of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) 80 km northeast and 1,617 km southeast of the crater (Brown et al 2008;Le Pichon et al 2008). Azimuth and entry angle derived from the observed signal time sequences and back azimuths were estimated to be 110° and 50° from the horizontal (Le Pichon et al 2008).…”

“…Brown et al (2008) derived an azimuth of 82° and an entry angle of 63°. While Le Pichon et al (2008) expect an initial energy release during atmospheric entry in the range of 1-8 kt TNT equivalent (4,200-33,000 GJ), Brown et al (2008) estimate 0.06-0.32 kt TNT equivalent (250-1,300 GJ). Both studies infer a rather low atmospheric entry speed of the meteoroid in the order of 12 kms −1 (Brown et al 2008;Le Pichon et al 2008).…”

“…These results correlate with data obtained by geologic surveying of the crater, namely steep crater slopes and enhanced ejecta thickness along the rim of the terrace, and gentle crater slopes with a reduced ejecta thickness at the rim along the creek bed. In a second model, we changed the impact azimuth to 90° (impact towards W) (Brown et al 2008;Le Pichon et al 2008) and assumed an impact angle of 40° (see next paragraph). The final crater shape and distribution of ejecta is shown in plane view (Fig.…”

“…Azimuth and entry angle derived from the observed signal time sequences and back azimuths were estimated to be 110° and 50° from the horizontal (Le Pichon et al 2008). Brown et al (2008) derived an azimuth of 82° and an entry angle of 63°. While Le Pichon et al (2008) expect an initial energy release during atmospheric entry in the range of 1-8 kt TNT equivalent (4,200-33,000 GJ), Brown et al (2008) estimate 0.06-0.32 kt TNT equivalent (250-1,300 GJ).…”