WARNING: NASA says the exercise was to prepare for a 2020 collision

The space agency has been working with the US Federal Emergency Management Agency to prepare.

And according to NASA scientist Thomas Zurbuchen, “it’s not a matter of if but when” the impact comes.

In the current training scenario, the asteroid is 100% certain to hit Earth and cannot be deflected with a missile.

The theoretical impact takes place on September 20, 2020, when it slams into the US state of California or the waters offshore.

This means a mass evacuation of the metropolitan Los Angeles area became necessary and population displacement models had to be worked out.

As part of their efforts, the two agencies calculated as well the impact footprint, the effect on infrastructure, and other realistically calculable data.

The exercise on October 25 in El Segundo, California, also explored the best way to quickly update the public while combatting misinformation.

FEMA Administrator Craig Fugate said: "It is critical to exercise these kinds of low-probability but high-consequence disaster scenarios.

"By working through our emergency response plans now, we will be better prepared if and when we need to respond to such an event."

Dr Zurbuchen of NASA’s Science Mission Directorate in Washington, said: ”It's not a matter of if – but when – we will deal with such a situation.

"But unlike any other time in our history, we now have the ability to respond to an impact threat through continued observations, predictions, response planning and mitigation."