How Much Of A Threat Are Asteroids?

Our solar system is home to countless asteroids and other forms of planetary debris. With so many asteroids in the solar system, they inevitably collide with the planets from time to time. Every planet in the solar system experiences asteroid impacts, and the Earth is no exception. Asteroids can pose a significant threat to life on Earth, with the size of the asteroid determining whether it could cause an extinction level event. The last major asteroid impact on Earth was around 65 million years ago, when an asteroid around 6 to 9 miles (10 to 15 kilometres) wide struck the Earth in what is now the Yucatan Peninsula. The resulting impact was truly apocalyptic, eventually wiping out over 75% of all life on Earth, including the dinosaurs. If such an event were to happen today, it would likely mean that end of our civilization and of human life. How likely is it that such an event could happen again?

Near Earth Asteroids

The asteroid Bennu is classified as a near-Earth asteroid that could potentially become a threat to the Earth in the far future, NASA

Space agencies from around the world actively track what are called near-Earth asteroids. These are asteroids that are located within Earth’s vicinity, and they pose more of a threat to our world than other asteroids. As of 2021, there are 26,115 known near-Earth asteroids, 2,000 of which are potentially dangerous to the Earth. Of those 2,000, 158 are larger than one kilometre wide, meaning they could potentially cause an extinction level event. Thankfully, none of these asteroids pose an immediate or significant threat to our planet. Of all the potentially dangerous near-Earth asteroids, none have a greater than 1% chance of impacting our world. 

How Often Do Asteroids Impact Earth?

    The asteroid Vesta is far enough away that it poses no risk to life on Earth. NASA

Large asteroids, such as the one that killed the dinosaurs, do not strike the Earth often. On average, the Earth will experience one large asteroid impact every 100 million years or so. Since the last one hit the Earth 65 million years ago, we have about 35 million years before we’re due for another impact. Even if a large asteroid were suddenly heading towards the Earth, NASA has developed plans to deflect such an asteroid. Unlike in a lot of movies, we cannot simply blow an asteroid apart. Blowing up an asteroid would not significantly change its trajectory, and the Earth would still be pummeled by the asteroid’s debris. Rather, humanity would have to deflect the asteroid and place it in a new orbit. Thankfully, NASA is already testing this method on asteroids. In November 2021, NASA launched the Double Asteroid Redirection Test (DART) on a mission to impact an asteroid. DART is currently heading towards an asteroid that is orbited by a smaller asteroid. The goal of DART is to crash into the smaller asteroid and alter its orbit around its larger companion. If the mission is successful, it will prove that we have the technological capability to potentially deflect an Earth-threatening asteroid.