NASA has carried out an emergency drill simulating the impact of an asteroid hitting earth in 2020.
Their latest simulation had scientists in California preparing to evacuate 18 million people from Los Angeles under the threat of an 800-foot wide space rock hitting the US coastline.
NASA and FEME (Federal Emergency Management Agency) worked together on the scenario.
Auckland University Astrobiologist Kathy Campbell joined Paul Henry this morning to discuss why these simulations are carried out.
She said scientists were keeping a "super close eye" on the asteroids travelling around space, and once they got larger than a kilometre in diameter, red flags were raised.
So scientists could "divert or destroy" an asteroid headed towards earth, they needed as much as 18 months to a decade of warning time.
"Anything even the size of a car hits at supersonic speeds can cause huge havoc if it hits in the middle of a city"
"We need some time to scramble"
Dr. Campbell said these types of exercises were similar to the volcano drills run by Civil defence and Auckland University.
This Discovery Channel simulation demonstrates what would happen if an asteroid did hit earth, which they say has happened at least six times in earth's history.