[Reading Science] "Even a graze causes serious injury"... Asteroids and space debris, low probability but deadly

▲Imaginary image of an asteroid colliding with Earth. [Photo by NASA]

[Asia Economy Reporter Kim Bong-su] How much of a threat do falling asteroids and space debris pose? Although the probability is low, they are analyzed to cause massive damage.

◇How dangerous is it?

The probability is relatively low. Most burn up during atmospheric entry. The rest disintegrate around an altitude of 78 km. However, although rare, significant damage can occur. On February 13, 2013, an asteroid about 17?20 meters in size that fell in Chelyabinsk, Russia, caused a shockwave equivalent to approximately 600 kt of TNT, resulting in 1,613 injuries and the destruction of 7,320 buildings. For asteroids, those under 10 meters have a probability of occurrence once every 10 years, under 30 meters once every 100 years, and under 140 meters once every 5,000 years. Artificial objects are similarly dangerous. The heaviest object that has fallen and remained on the ground so far weighs 250 kg, and considering its speed (50 m/s), it has tremendous destructive power. However, the probability remains low. It is estimated that over 100 years, about one person worldwide will be harmed by falling space objects.

◇How is it dealt with?

If the fall of a space object is anticipated, established manuals are activated domestically and internationally. In the case of natural space objects, if the probability exceeds 1 in 10,000, the president is notified, and response measures are taken according to disaster levels such as ‘interest,’ ‘caution,’ ‘alert,’ and ‘serious.’ Artificial space objects are treated similarly.

If a large asteroid approaches Earth, as depicted in the movie ‘Deep Impact,’ a global state of readiness is activated. The United Nations monitors asteroids through the International Asteroid Warning Network (IAWN) under the Committee on the Peaceful Uses of Outer Space (COPUOS). At the annual Planetary Defence Conference held by the International Academy of Astronautics (IAA), experts from various countries gather to create scenarios. Experts believe that launching nuclear missiles at asteroids is the only countermeasure. The problem lies with small asteroids that are difficult to observe. Dr. Cho Jung-hyun of the Korea Astronomy and Space Science Institute explained, “Small ones can only have their impact locations predicted 1 to 2 months in advance, so there is nothing that can be done,” adding, “They need to be discovered at least 2 to 5 years in advance.”