Astronomers estimate a 1 percent risk that the space rock will collide with our planet on April 27, 2027. What must we do?
It is this potentially catastrophic scenario that 300 astronomers, scientists, engineers and emergency experts apply their collective minds to this week in a suburb of Washington, the fourth such international effort since 2013.
"We need to make people understand that this is not Hollywood," said NASA administrator Jim Bridenstine when he opened the sixth international planetary defense conference on the University of Maryland campus in College Park.
Represented countries are China, France, Germany, Israel, Italy, Russia and the United States.
The idea that one day the planet must defend itself against an asteroid that is used to elicit what experts call a & # 39; giggle factor & # 39; to mention.
But a meteor that erupted above the atmosphere over Russia on 15 February 2013 helped to put an end to the abusive words.
That morning a star-shaped star shape of 20 meters appeared out of nowhere above the southern Urals, exploding 14 miles (23 kilometers) above the city of Chelyabinsk with such force that it shattered the windows of thousands of buildings.
A thousand people were injured by the shards.
But "the positive aspect of Chelyabinsk is that it made the public aware, made the political decision makers aware," Detlef Koschny, co-manager of the European Space Agency's (ESA) Planetary Defense Agency, told AFP.
Only those asteroids whose orbit around our sun brings them within 31 million miles of our planet – defined as "near the earth" – are of interest.
Astronomers find new ones every day: more than 700 so far this year, for a total of 20,001, said Lindley Johnson of NASA & # 39; s Planetary Defense Coordination Office, founded in 2016.
One of the riskiest is a rock called 2000SG344: 165 feet in diameter, with a probability of 2,096 of invading the earth within a hundred years, according to the ESA.
The majority are very small, but 942 are more than 1 km wide, astronomer Alan Harris estimates.
The scientist told an audience that some large ones are probably still outside: "A large part of the largest ones are hiding … actually parked behind the sun."
They are mainly found by two American telescopes, one in Arizona and the other in Hawaii.
The ESA has built a telescope for this in Spain and is planning others in Chile and Sicily.
Many astronomers demand a space telescope because terrestrial telescopes cannot detect objects on the other side of the sun.
This week's exercise attempts to simulate the global response to a catastrophic meteorite. The first step is to focus telescopes on the threat to accurately calculate the speed and trajectory, according to rough initial estimates.
Then it comes down to two choices: try deflecting or evacuating the object.
If it is less than 165 feet, the international consensus is to evacuate the threatened region. According to Koschny, it is possible to predict the country that it will strike two weeks ahead. Days away from impact, it can be reduced to within hundreds of miles.
What about larger objects? Trying to forge them into horror elements like in the movie Armageddon would be a bad idea, because it could just make smaller but still dangerous pieces.
The plan, on the other hand, is to launch a device to the asteroid to cover its orbit – such as a cosmic bumper car.
NASA plans to test this idea on a true asteroid 492 feet across, in 2022, with the Double Asteroid Redirection Test (DART) mission.
An issue that remains is politics, says Romana Kofler of the United Nations Office for Outer Space Affairs.
"Who would be the decision-making authority?" she asked. "The consensus was to omit this aspect."
The United Nations Security Council would probably be convened, but it is an open question whether rich countries would finance an operation if they themselves were not close to 2000SG344 or another sky rock.