[오늘은] What are the chances of an asteroid impacting Earth?

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(Seoul = Yonhap News) In February 2013, a large flash of light flashed in the sky of the Chelyabinsk Oblast near the Ural Mountains, Russia, and with a loud explosion, small burning objects flew through the sky and fell to the ground with white smoke.

Thousands of houses and factories were destroyed, and more than 1,000 people were injured, but fortunately there were no fatalities.

It was the asteroid that caused this disaster. An asteroid with a diameter of 17 to 20 meters exploded in the sky, and debris fell and caused damage.

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Today is International Asteroid Day. It was officially designated by the United Nations in 2016 to notify the risk of an asteroid impact and to request the international community to respond to it.

June 30 is also the day that an asteroid with a diameter of 50 meters exploded over Tunguska, Siberia, Russia in 1908, devastating 2,000 square kilometers of forest.

◇ What is an asteroid?

Asteroids are celestial bodies that revolve around the sun like planets such as Earth and Mars, but are smaller in size. In the early stages of the formation of the solar system, it can be said that it is the debris that does not become a planet and drifts in space.

They are located mainly in orbits between Mars and Jupiter, and their number is innumerable. Most are less than 50 km in radius, but there are some very large ones, such as the ‘Ceres’ with a diameter of 914 km.

Asteroids are mainly composed of rocks and metals. It’s different from a comet, which is a mass of ice mixed with dust and gas.

What we commonly call a ‘shooting star’ (meteor) is a phenomenon that occurs when residues from asteroids or comets or dust from the solar system burn in the Earth’s atmosphere.

◇ Asteroids threaten the Earth?

The scientific community calls an asteroid with a diameter of 140 m or more that approaches the Earth within about 7.5 million km and is a ‘potentially threatened asteroid’ (PHA), and it is estimated that there are about 2,000 PHAs.

The problem is that the closest celestial body to the Earth is within 48 million km. Of these, large asteroids with a diameter of 1 km or larger have been virtually identified, but many of the smaller asteroids have not been identified. You never know when it will collide with Earth.

According to the scientific community, an asteroid with a diameter of 100 m could devour a city, and if it was 1 km in diameter, it could cause irreparable consequences for the Earth’s ecosystem.

The most threatening asteroid identified so far is ‘Benu’. An asteroid with a diameter of 490 m and a mass of about 140 million tons. However, the probability of a collision with the Earth doesn’t seem very high, 1 in 1750 by 2300. September 24, 2182 was the day with the highest risk of collision.

Scientists say that none of the currently known near-Earth asteroids or comets could collide with Earth within 100 years. Of course, this means that only the trajectory has been identified.

◇ Why do asteroid exploration?

Asteroids are also the object of human exploration. It is believed that the answer to the planet formation and the origin of life may be found in asteroids that retain the early appearance of the solar system.

The National Aeronautics and Space Administration (NASA) has been exploring the asteroid’s surface since 1991. In May of last year, the Osiris-Rex probe returned home with a sample of the near-Earth asteroid ‘Benu’, and in October, the probe Lucy embarked on a 12-year long expedition to explore a total of eight asteroids.

In 2020, Japan’s Hayabusa 2 brought samples taken from the asteroid ‘Ryugu’ to Earth, and China will launch a probe in 2024 to land on the asteroid ‘Kamo Oalewa’ to collect samples, and then return to Earth in 2026. It is said to be delivered.

In the case of Korea, the Korea Astronomy and Space Science Institute decided to directly explore the asteroid ‘Apophis’ passing by the Earth in 2029, but it was unfortunately canceled because it was recently rejected in the process of selecting a project for a preliminary feasibility study (Yetta).

After the successful launch of the Nuri (KSLV-Ⅱ), Korea, which has risen to the ranks of the ‘seven major space powers’, is also expected to explore asteroids and unravel the mysteries of the universe.

By Lim Dong-geun, by Lee Hee-won, intern reporter

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2022/06/30 06:00 Send