Asteroids are not as rare as we might think – in fact, there are at least 1.4 million of them floating around the solar system that we know of. However, most of these asteroids are located in the main asteroid belt between Mars and Jupiter. Near Earth Objects (NEOs) are a subset of asteroids whose orbits cross Earth’s path around the sun, posing a potential threat to our planet.
But how often do these asteroids actually come close to Earth? The frequency of near-Earth asteroids depends on their size. Smaller asteroids, like dust particles that burn up in Earth’s atmosphere, pass by us every day. Larger rocks, such as those the size of a few beach balls, come close many times per year and occasionally yield meteorites. Even semi-truck-sized objects only hit Earth two to three times per century, with most impacts occurring over the ocean.
The biggest asteroids, over 140 meters across, are the rarest and pose the most significant threat. Although their impacts are infrequent, they can cause significant local or regional damage, including tsunami risks if they strike the ocean. Luckily, the probability of such impacts occurring in a human lifetime is low, but not zero. Astronomers have already tracked about 40% of the asteroids in this size range.
The asteroid that killed the dinosaurs was thousands of meters in diameter, making it an exceedingly rare occurrence. While there is a fairly large asteroid, Apophis, headed our way in the near future, the risk of it actually hitting Earth is quite low. Astronomers are constantly monitoring and preparing for potentially threatening asteroids, with missions like the NASA Double Asteroid Redirection Test (DART) demonstrating the technology needed to push an asteroid off a collision course.
One of the challenges in planetary protection is identifying potential threats early. Just recently, two large asteroids swung by Earth, with one discovered only a week before its close approach. Discovering these asteroids is a difficult task due to the constant movement of Earth and the asteroids themselves. Large telescopes and space telescopes like the Vera Rubin Observatory and NEO Surveyor are being developed to scan the sky regularly and identify potentially hazardous asteroids.
Overall, astronomers are taking the asteroid survey challenge seriously to ensure our asteroid future is secure. With ongoing efforts to discover and track asteroids, we can better prepare for any potential impacts and take necessary actions to protect our planet.
