Asteroids are directly responsible for or partly involved in at least three mass extinctions recorded in Earth’s history.
A representative of them is an asteroid that landed in Chixulub, Mexico, at the end of the Cretaceous period 66 million years ago, ending the age of dinosaurs and causing the extinction of 75% of all living things on the planet.
‘Dimorphos’, which NASA conducted a collision test with the ‘Dual Asteroid Orbital Correction Experiment’ (DART) spacecraft this time, is about 160m in diameter, which is not much.
However, it is known to have enough destructive power to turn any city into ruins.
Considering the fact that the asteroid that exploded over Chelyabinsk, Russia in February 2013, smashing windows in six cities and injuring 1,600 people, was only 18 meters tall, the danger can be fully guessed.
Asteroids are remnants of rocks that the solar system used to form planets about 4.6 billion years ago, and vary in shape, size, and composition.
Most of them orbit the Sun while being concentrated in the asteroid belt between Mars and Jupiter, but they collide with each other due to the gravitational action of Jupiter and are pushed toward the inner planets including Earth.
Once in this inner planet’s orbit, it orbits for millions of years before colliding with the sun or inner planet, or being pushed back into the asteroid belt or beyond.
Scientists are currently focusing on near-Earth celestial bodies approaching the Earth within 30 million miles (48 million km) and asteroids with orbits that intersect Earth’s orbit.
It is estimated that there are about 26,000 near-Earth celestial bodies larger than 140 meters in size.
It is estimated that the 140-meter-diameter asteroid can create a crater of about 1 to 2 kilometers and can devastate a large city and cause mass casualties.
Asteroids with a diameter of more than 1,000m will form a crater of 10km, and asteroids with a diameter of more than 10km will form a crater of 100km, which is analyzed to lead to the collapse of civilization and the mass extinction of terrestrial life, respectively.
It is calculated that there is a probability that a 1,000-meter-class asteroid will collide with Earth about once every 500,000 years, and a 10-km-class asteroid has a chance of impacting once every 100 million to 200 million years.
Fortunately, 95% of asteroids over 1,000 meters (about 900) have been identified, and all four asteroids greater than 10 kilometers are being tracked and managed.
The problem is that it is estimated that there are about 25,000 140m-class asteroids that can collide once in about 20,000 years, but only 10,000 have been confirmed at present.
The remaining 15,000 must be tracked forward to see if there is a risk of collision.
In 2005, the U.S. Congress required NASA to find more than 90% of asteroids larger than 140m that could threaten the Earth, but only one is found every day, so it is expected that it will take another 30 years.
Fortunately, none of the asteroids discovered so far are in danger of colliding with Earth within the next century.
It is estimated that there are about 5 million asteroids with a diameter of 25 meters that can collide with Earth once every 100 years, but only 0.4% have been discovered so far.
An asteroid of this size can cause an aerial explosion similar to that of Chelyabinsk, and if it occurs in a densely populated area, injuries can occur one after another.
There are about 500 million asteroids with a diameter of 4m, and only 0.1% of them have been discovered, but they only cause a flash of light once a year, so there is no need to worry.
In July 2019, the ‘2019 OK’ asteroid, estimated to be 50-130 m in diameter, passed by about 73,000 km from the Earth. can be estimated
If this asteroid collided with Earth, it was estimated that somewhere up to 80 km in area would have suffered damage.
/yunhap news