Simultaneously, the menace asteroids pose to Earth cannot be overlooked. The elimination of dinosaurs about 65 million years ago due to an asteroid strike stands as a solemn reminder of this.
In statistical terms, the chances of Earth being hit by an asteroid are directly linked to the size of the asteroid. Every day, Earth is bombarded by tiny space dust particles, which burn up to create meteors or "shooting stars" upon entering our atmosphere.
Asteroids with diameters in the tens of meters are believed to hit the Earth roughly once each century. The last two instances of such events were both in Russia - the Tunguska event in 1908 and the Chelyabinsk event in 2013. Both asteroids measured about 20 meters in diameter and exploded in the atmosphere before reaching the ground. The ensuing detonations caused extensive damage, with the Siberian wilderness being set ablaze in the first instance, and considerable infrastructural damage and injuries resulting from shattered window glass in the second.
Impacts involving asteroids of a kilometer or more in diameter are extremely rare, occurring roughly every few tens of millions of years. The most recent such event, which led to the extinction of the dinosaurs, involved a 5 km asteroid and resulted in a global shift in climate for several years, challenging the resilience of life on Earth.
The primary threat to Earth currently does not come from these larger asteroids. At this point, we have identified most near-Earth asteroids of about a kilometer in diameter, and none of them pose a risk of colliding with our planet. The real concern lies with smaller asteroids, like the one that hit Chelyabinsk, which are often only detected when they are dangerously close to Earth or not discovered at all.
One of the key goals of planetary defense, therefore, is to upgrade our telescope network to detect these smaller asteroids, with the aim of preventing future events like the 2013 Chelyabinsk incident.
Credit: Alex Alishevskikh.
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