Thought folks here might like to see this. patrick Asteroid Threat Exercise at PDC Meeting by David Morrison Over the 5 days of the Planetary Defense Conference in Frascati, the attendees participated in an imaginary impact scenario. The fictional asteroid 2015PDC followed an orbit carefully planned by Paul Chodas (JPL); Mark Boslough (Sandia) modeled the probable effects of impacts over land and sea, and Debbie Lewis (Axiom) stage-managed the exercise. The scientists attending the meeting provided regular strategy inputs to the “world leaders” on how to deal with the possibility of an impact on September 3, 2022. Many volunteered for role-playing to represent the reactions of political leaders and the public. The exercise began on Day 1 of the conference with the announcement, dated June 9, 2015, of discovery of 2015PDC (a fictitious asteroid with diameter between 150 and 450m) and its predicted close pass by Earth seven years in the future. On Day 2 it was announced that new observations had improved knowledge of the orbit and now predicted a 50% chance of impact, and by December 2016 (18 months after discovery) an impact was certain. Although the exact location could not be determined, the locus of possible impact points was defined by a “risk corridor” that stretched from the Pacific Ocean, across the South China Sea, and into the South Asian mainland. Cities lying close to this path included Manila, Hanoi, Dhaka, Delhi, and Tehran. Here the role-playing began, with the realization that the areas at risk were all in Asia, and that a majority of the world’s Moslems were living along the risk corridor, while most of the decision-making would likely be done in Europe and the United States. The only two nations along risk corridor with substantial space capabilities were China and India. By summer 2019 the risk corridor had shrunk to within the South China Sea. While there could be potential tsunami damage to the nations around this body of water, large population centers such as Dhaka and Delhi were spared. In spite of the reduced risk, the US, ESA, and Russia proposed to launch several kinetic impactor (KI) missions in the only available window in August 2019. This information precipitated the major crises of the exercise, since any KI effort that was not fully successful in moving the target area off the Earth could move it into the heavily populated parts of India and Bangladesh. Thus some nations wanted to take the hit and deal with the resulting tsunami, while others opted for the KI attempts. We faced the new threat of possible warfare between China and India. The adopted scenario did include the launch of several KI missions, but the deflection was only partially successful. The asteroid split, with one part missing the Earth, while a 100m fragment was still headed for the Ganges and Brahmaputra deltas, including the cities of Delhi and Dhaka. Having tried to deflect the asteroid, we were now dealing with a human-made threat rather than an “act of god”, with associated issues of liability and compensation. India unilaterally decided to attempt a last-minute nuclear strike on the asteroid, but this mission failed. The exercise concluded with asteroid impact near Dhaka on September 3, 2022. Was this a realistic simulation of an impact threat? The answer is yes, for the orbit of the asteroid and the limited windows for telescopic and radar observations. But the political leaders were being played by scientists with no prior expertise on the nations involved, so their assessments and decisions were strictly amateur. In any case, it was educational for the participants. We got a much better idea of how difficult it would be to measure size and physical properties, and how few opportunities there would be for spacecraft or radar observations, in the case where the asteroid picked us, not the other way around. And it illustrated that while we talk about defending the planet, in a real case individual nations will likely have conflicting priorities on how to deal with the threat.