How would we respond to an imminent asteroid strike? Do we have the tools to mitigate it? What advancements are needed? A team of experts tackled these critical questions in NASA's latest planetary defense exercise.
No known asteroids currently threaten Earth in the foreseeable future, yet the unpredictable nature of celestial mechanics demands vigilance. NASA's Center for Near-Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory recently concluded its seventh biennial planetary defense simulation, engaging U.S. and international partners in a realistic impact scenario.
Participants assumed roles such as NEO observers, space agency officials, emergency managers, and decision-makers. Their mission: collaborate to assess and respond to an evolving asteroid threat.
Full details of the exercise are available on the CNEOS website. The fictional asteroid, "2021 PDC," was discovered on April 19, 2021, at 57 million km from Earth, with closest approach set for October 20, 2021—just six months away.
Initial impact probability stood at 1 in 2,500, based on only two days of observations. Size estimates ranged from 35 m to 700 m.
The scenario escalated rapidly. By day one, the impact probability surged to 1 in 20 (5%). For context, a real-world coordinated response activates at 1 in 100.
On day two, the probability reached 100%, with impact confirmed for October 20 somewhere in Europe or North Africa. Size remained uncertain.
The team explored mitigation options, including nuclear deflection. Ultimately, they concluded that, in this timeline, humanity lacks the capability to prevent the impact—no mission could launch and intercept in time.
Two months into the simulated timeline, the impact zone narrowed to a 800 km by 250 km area over power plants in Europe, affecting Germany, Czech Republic, Austria, Slovenia, and Croatia. Asteroid size refined to about 140 meters.
Risk assessments showed a 21% chance of over one million casualties and 74% chance of over 100,000. In the worst case, 6.6 million people could be impacted within 250 km of ground zero.
Days 4 and 5 refined the exact location further.
These exercises sharpen our readiness. Experts emphasize enhanced detection via NASA's NEO Surveyor, ESA's Test-Bed telescope in Chile (now operational), and the Flyeye telescope under construction in Italy to reduce uncertainties and bolster defenses.
