NASA and ESA ran an asteroid impact simulation. Nobody could stop it from hitting Europe.
In a weeklong tabletop exercise, planetary defense experts had six months of warning and still concluded no spacecraft could launch in time to deflect the hypothetical asteroid.
NASA and the European Space Agency ran a weeklong tabletop exercise simulating the discovery and approach of a hypothetical asteroid, code-named 2021 PDC, and concluded that with the time available, no spacecraft could realistically be launched to deflect it before it struck Europe, according to reporting on the exercise by IFLScience and Big Think.
The scenario unfolded over the several days of the exercise as fictional new observations refined the threat. On the first day, astronomers in the scenario discovered the object with only a 5% probability of impact, estimated at somewhere between 35 and 700 meters across, with a target zone covering roughly two-thirds of the planet — Southeast Asia, Australasia and Antarctica were the only regions the fictional models ruled out. One week later, in the scenario's timeline, the impact was confirmed as certain, narrowed to Europe or North Africa, and mission designers concluded deflection was no longer practical given the asteroid's speed and how close it already was, according to IFLScience's reporting.
By the third simulated day, set two months later, the fictional impact zone had narrowed further to a region spanning Germany, the Czech Republic, Austria, Slovenia and Croatia, with the object's size estimate refined to between 35 and 500 meters and as many as 6.6 million people potentially in the affected area. In the exercise's final phase, the hypothetical object was refined to about 105 meters across, with the impact zone converging on the Czech Republic-Germany-Austria border region — reporting on the exercise noted the eventual on-the-ground discussion turned to evacuation planning in an area south of Prague.
The takeaway the exercise was built to produce
Participants in the scenario concluded that the fictional warning time, even at nearly six months, was too short to mount a deflection mission with current capability. "If confronted with the 2021 PDC hypothetical scenario in real life we would not be able to launch any spacecraft on such short notice with current capabilities," the exercise's participants concluded, according to IFLScience's account of the tabletop exercise, which was conducted at that year's Planetary Defense Conference.
The exercise was designed from the outset to be unsolvable within the fictional timeline, a standard feature of planetary-defense tabletop exercises meant to stress-test coordination between space agencies and civil authorities rather than to model a scenario NASA or ESA consider imminent. No real asteroid discovery or impact threat was involved.
US In News compiled this archived account from contemporaneous coverage by IFLScience and Big Think of the NASA/ESA planetary defense tabletop exercise. It restores a story originally published on this site in 2021; figures are as reported at the time.