A group of space researchers came together to test out what would happen if Earth were hit by an asteroid. The results of the planetary defense exercise that took place last year have just recently been published and show the steps that would need to be taken.

The participants thought of asteroid Apophis. The asteroid will come close to Earth in 2029 and 2068 but won't hit the planet. For the purpose of the exercise, the participants worked out what could have happened if it had threatened Earth.

Clockwise from top left are three of the observatories that participated in a 2021 planetary defense exercise: NASA’s Goldstone planetary radar, the Mount Lemmon telescope of the Catalina Sky Survey, and NASA’s NEOWISE mission. At bottom left is an illustration of the path of Apophis’ close approach in 2029.
Clockwise from top left are three of the observatories that participated in a 2021 planetary defense exercise: NASA’s Goldstone planetary radar, the Mount Lemmon telescope of the Catalina Sky Survey, and NASA’s NEOWISE mission. At bottom left is an illustration of the path of Apophis’ close approach in 2029. NASA/JPL-Caltech/University of Arizona

This real world scientific input stress-tested the entire planetary defense response chain, from initial detection to orbit determination to measuring the asteroid's physical characteristics and even determining if, and where, it might hit Earth.

The asteroid was tracked using NASA's Near- Earth Object Wide-fieldInfrared Survey Explorer mission, which gathered information on its size and shape. Simulations of possible impact locations on Earth were used to estimate how much damage would be done by an impact. Disaster agencies might be able to use this data to help them in the case of an asteroid.

Michael Kelley is a program scientist with the Planetary Science Division of NASA. When many of the exercise participants were forced to work remotely, we were able to find out more about a potential hazard. The exercise went well.

The results are in a journal.

There is a recommended video.