Speaker
Description
A hypothetical asteroid-impact scenario (http://neo.jpl.nasa.gov/pdc25/) will be used as the basis for discussion and analyses during the PDC 2025 table-top exercise. The asteroid is “discovered” on June 5, 2024, and is classified as a potentially hazardous asteroid with a diameter initially estimated between 90-160 meters with a median size of 125 meters and a full-size range of 50-280 meters. The large size uncertainty is due to uncertainties in both albedo and absolute-magnitude values. Based on the range of possible Earth impact velocities of 2024 PDC25 in 2041 and its estimated size and taxonomy, the energy released at impact is estimated to be most likely in the range 5 - 70 Mt, but possibly as large as 720 Mt. The expected damage of the impacts could be on the regional scale, likely extending as far as 110-200 kilometers from the impact location. The impact risk-corridor wraps more than halfway around the globe, cutting through Eastern Europe, the Mediterranean Sea, through central Africa to the Cape of Good Hope, across the South Atlantic to the Antarctic coast near the Antarctic Peninsula, and then into the South Pacific. Therefore, we focused our numerical simulation efforts on reflecting water, land, and ice portions of the impact corridor. Firstly, water impacts at a few locations at the Barents Sea, Mediterranean Sea, and South Atlantic & South Pacific oceans are simulated. Because most of the potentially affected South Africa’s False Bay region is heavily populated, we have conducted several high-resolution water-wave heights along the coastline under different conditions of the asteroid diameter & impact location uncertainties to assess flooding hazards and consequences. Secondly, for land impact and consequences, we numerically characterized the crater formation at impact locations given different geological conditions for different countries along the risk-corridor. Thirdly, we simulated numerically the impact of the asteroid on ice along West Antarctica to access the ice-sheet fracturing, melting and their consequences on global ocean circulation. Lastly, we simulated the airburst of the asteroid on two South Africain regions Stellenbosch & Cape Gate to assess the airburst pressure damage as function of airburst height and size of the asteroid. The impact of the asteroid with land, water and ice is simulated using the hydrocode GEODYN, creating a wave source for the Boussinesq-based water-wave-propagation code, WWP which has been used to predict the consequences of previous PDC & FEMA hypothetical exercises. For the ground motions propagation, the ground-impact source is coupled to the elastodynamic WPP code which has been used extensively by DOE. Airburst simulations have been conducted using solely by GEODYN. Impact of the asteroid on the global ocean circulations are being simulated using a new HPC exascale code called xGOC, not publicly released. We supplement the results at several stages with movies of asteroid impacts on different crustal emplacements using different asteroid impact velocities and angles.
Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52- 07NA27344.