CANCELLED: LPL Colloquium

Tuesday, Apr 15, 2014
3:45 pm
Location: Kuiper Space Sciences
Room: 312

Dr. Peter Brown
Professor and Canada Research Chair
Western University

The Chelyabinsk Airburst and what it tells us about small Near Earth Asteroids and the Impact Hazard

Abstract:
At 03:20 UT (09:20 local time) on Feb. 15, 2013 a bright, long-lasting fireball was widely observed over the region of Chelyabinsk, Russia. This event was of such large energy and deep atmospheric penetration that the shock wave reaching the surface had sufficient overpressure to blow out windows, doors and cause light structural damage particularly in the region near the city of Chelyabinsk. Close to 1500 people were injured by flying debris (mainly broken windows) as a result of the shock wave. The energy of the event has been estimated from several independent techniques to be approximately 500 kT of TNT equivalent. The airwave from the airburst was recorded by infrasound sensors over the entire globe; some acoustic records show the airwave circling the planet for nearly three days after the event. The range of energy yields translates into a meteoroid with a mass of order 12 000 tonnes and diameter of approximately 19m. This fireball is the most energetic confirmed airburst since the Tunguska fireball of 1908. Chelyabinsk's energy, fragmentation behaviour and trajectory have been well measured thanks to video recordings by hundreds of vehicle dashcams. Together with measurements of the associated surface blast effects it provides an important baseline for interpretation of the effects of future impactors and also provides calibration for better interpretation of past events such as Tunguska. In this talk I will compare predictions for Chelyabinsk-like impacts made by existing entry models with actual observations of the Chelyabinsk airburst as well as infer the physical structure of the original asteroid based on its ablation behaviour in the atmosphere.

Host: Tim Swindle