On Dec. 3, the small asteroid COWECP5 streaked into Earth's atmosphere and exploded in a fiery display above Siberia. While the event was dramatic, it was ultimately harmless because the space rock was only 70 centimeters across and disintegrated before it could cause any damage.
But for people who study asteroids, this near-miss was a stark reminder of the dangers lurking in the cosmos. What if that asteroid had been bigger? What if it had been a "city killer?" Earth is far more vulnerable to asteroid impacts than most people realize, and the systems in place to protect the planet are far from perfect.
The National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) are tasked with keeping an eye on Near-Earth Objects (NEOs), the term used for asteroids and comets that come dangerously close to the planet.
These agencies have sophisticated telescopes and advanced tracking systems, but the reality is that they can’t monitor the entire sky all the time. The Siberian asteroid was only spotted by a NASA-funded telescope in Arizona seven hours before it hit Earth. While that might sound like plenty of time, it is actually a dangerously short window.
If the asteroid had been larger, it could have caused significant damage on the ground. And if it had been a true "city killer," like the 400-meter-wide asteroid that astronomers feared would hit Earth on Christmas Day in 2004, seven hours would not have been enough time to evacuate millions of people or devise a defense strategy.
The fact is, there simply are not enough professional astronomers and telescopes to cover every possible angle. Most of the world’s advanced telescopes are concentrated in a few regions, leaving vast "dark zones" where no one is watching.
This means that asteroids coming from certain directions — like over Japan or Russia — could slip through the cracks. While NASA and ESA are doing their best, they are fighting an uphill battle against the sheer number of space rocks out there.
Every day, Earth is bombarded by an estimated 100 tons of space debris, most of which burns up harmlessly in the atmosphere. But every now and then, something much larger and more dangerous appears.
Astronomers have identified 36,765 NEOs, including more than 11,000 that are over 140 meters across and 868 that are larger than a kilometer. Out of those NEOs, 1,714 are considered potentially hazardous, meaning there's a non-zero chance they could collide with Earth.
But even relatively small asteroids can cause catastrophic damage. The Chelyabinsk meteor, which exploded over Russia in 2013, was only 18 meters in diameter. However, it injured over 1,600 people and damaged more than 7,000 buildings.
Larger asteroids, like the one that narrowly missed Earth in 2004, could wipe out entire cities or even trigger global disasters.
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