NASA chief warned that it was time to take the threat of an asteroid to destroy Earth seriously.
Bridenstine spoke as the space agency began its planetary conference exercises, based on the hypothetical scenario of an asteroid effect.
NASA's director has expressed concern that similar warnings have historically brought amusement and said asteroid collisions were more common than they believed.
In this week's planetary defense exercises, which simulate a global response to a meteorite that destroys Earth, NASA's first step will be to accurately measure speed and orbit.
Then there has to be a decision: try to avoid the collision by diverting the asteroid, or clearing the area where it might crash.
Planetary defense and astronomical experts have warned humanity to destroy large asteroids with nuclear weapons out of concern that they simply shatter smaller dangerous pieces.
A scientific study published in March poured cold water on a film theory that humans could just blow up an asteroid on a collision course with the Earth, and found that the blast fragments from the asteroid would be It is likely to reform with it because of gravity.
The most likely response is to clear the area where the asteroid is likely to collide, especially if the asteroid is less than 50 meters (164ft) away.
Mr. Breedenstein noted three devastating asteroid effects that have occurred in the last century.
The last mentioned occurred in 2013, when a meteor exploded over the Russian city of Cheb Lybinsk, wounding hundreds of people.
It beat the sun for a moment, causing severe burns to the observers below, as well as smashing windows and buildings clattering.
A more solid rock would have caused greater damage and injury.
The meteor of Lybinsk was bright and warm when it was 18 kilometers above the earth. Its speed at this point was calculated at 40,000 km / h or 11.6 mph.
In other words, a rock that was initially the size of a two-story bus drove 20 times faster than a bullet.
It was the biggest object to hit Earth since the Tunguska incident of 1908, when a comet explodes or an asteroid destroyed 2,000 square kilometers of Siberian forest.
Mr. Breedenstein warned that one model suggests that similar asteroids could occur every 60 years, and that Hollywood offered a false sense of security by suggesting that humanity could save itself.