An entry model for the Tagish Lake fireball using seismic, satellite and infrasound records

• Published in: Meteoritics & Planetary Science
• Main Authors: Brown, Peter G., ReVelle, Douglas O., Tagliaferri, Edward, Hildebrand, Alan R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2002
• Subjects: Tagish; Tagish Lake
• Online Access: http://dx.doi.org/10.1111/j.1945-5100.2002.tb00846.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1945-5100.2002.tb00846.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.2002.tb00846.x

Abstract— We present instrumental observations of the Tagish Lake fireball and interpret the observed characteristics in the context of two different models of ablation. From these models we estimate the pre‐atmospheric mass of the Tagish Lake meteoroid to be ˜56 tonnes and its porosity to be between 37 and 58%, with the lowest part of this range most probable. These models further suggest that some 1300 kg of gram‐sized or larger Tagish Lake material survived ablation to reach the Earth's surface, representing an ablation loss of 97% for the fireball. Satellite recordings of the Tagish Lake fireball indicate that 1.1 times 10 12 J of optical energy were emitted by the fireball during the last 4 s of its flight. The fraction of the total kinetic energy converted to light in the satellite pass band is found to be 16%. Infrasonic observations of the airwave associated with the fireball establish a total energy for the event of 1.66 ± 0.70 kT TNT equivalent energy. The fraction of this total energy converted to acoustic signal energy is found to be between 0.10 and 0.23%. Examination of the seismic recordings of the airwave from Tagish Lake have established that the acoustic energy near the sub‐terminal point is converted to seismic body waves in the upper‐most portion of the Earth's crust. The acoustic energy to seismic energy coupling efficiency is found to be near 10 −6 for the Tagish Lake fireball. The resulting energy estimate is near 1.7 kT, corresponding to a meteoroid 4 m in diameter. The seismic record indicates extensive, nearly continuous fragmentation of the body over the height intervals from 50 to 32 km. Seismic and infrasound energy estimates are in close agreement with the pre‐atmospheric mass of 56 tonnes established from the modeling. The observed flight characteristics of the Tagish Lake fireball indicate that the bulk compressive strength of the pre‐atmospheric Tagish Lake meteoroid was near 0.25 MPa, while the material compressive strength (most appropriate to the recovered meteorites) was ...