Chances of an Asteroid Hitting Earth: Can It Destroy Us?

Our Planet Is Tougher Than We Might Think

For over 160 million years, dinosaurs ruled the planet until they met a sudden demise due to an unexpected visitor from space.

In other words, about 66 million years ago, an asteroid measuring at least 6 miles (10 km) in diameter dealt a devastating blow to the dinosaur world. The last asteroid to hit Earth with such catastrophic force triggered earthquakes, tsunamis, volcanic eruptions, and unprecedented climate disasters that quickly wiped out nearly 75% of all living creatures [1]. Fortunately, Earth itself survived the ordeal.

Does this mean our planet is more or less safe from an asteroid Armageddon? If the terrifying, dinosaur-killing space rock was not enough to bring about the end of the world, what would it take? Can an asteroid destroy Earth entirely—and how big would it have to be?

The short answer is that it would likely take a planet-sized rock to completely obliterate our world. However, destroying life on Earth—or at least the vast majority of it—would require significantly less.

It is widely known that an object roughly the size of Mars crashed into Earth early in its history, creating the Moon without destroying the planet itself [2].

Researchers frequently point to the giant-impact hypothesis, a scientific theory suggesting that a Mars-sized planet named Theia collided with Earth 4.5 billion years ago. This launched rocky debris into space that eventually coalesced into the Moon we see today. (Mars is about 4,200 miles or 6,700 km wide—more than 500 times wider than the asteroid that wiped out the dinosaurs.)

While experts debate whether this collision was a direct hit or a glancing blow, there is no doubt that if anything had been alive on Earth at the time, Theia would have wiped it out. (Scientists believe life may have emerged as early as 4.4 billion years ago, a few million years after the Theia impact.)

The Chances of an Asteroid Hitting Earth

As the mass extinction of the dinosaurs demonstrates, it takes far less force to severely impact life on Earth than it does to destroy the planet itself.

Interestingly, NASA considers essentially any space rock to be a potential hazard if it is at least 460 feet (140 meters) in diameter and orbits within 4.6 million miles (7.4 million km) of Earth.

According to NASA, an impact from a rock of this size could obliterate an entire city and undoubtedly devastate the surrounding region.

It is also worth noting that a collision with a larger rock—at least 0.6 miles (1 km) wide—would likely trigger the end of civilization and global climate catastrophes. Therefore, if a dinosaur-killing asteroid were to appear today, humans and countless other species would simply face extinction.

Generally speaking, the initial impact would create a massive fireball, killing everything in the immediate vicinity. Then, the impact dust and smoke from widespread fires would encircle the globe, ultimately plunging the planet into a deep freeze.

Furthermore, during this season of suffering, the sky would be so darkened by dust and noxious gases that plants would no longer be able to convert sunlight into energy through photosynthesis. This would cause plant life to die off worldwide, and animals would soon follow suit.

Identifying Threats and Planetary Defense

It is no secret that NASA and other space agencies take the threat of an asteroid impact very seriously, closely monitoring thousands of potential impactors in our solar system. The good news is that there is no known threat of a potentially hazardous asteroid hitting our planet for at least the next 100 years. If you are wondering, is the asteroid going to hit Earth in 2029, experts confidently say no. Furthermore, the chance of an asteroid hitting Earth in 2032 is virtually zero, as astronomers have definitively ruled out these previously feared impacts.

Ultimately, if a potentially hazardous space rock were to unexpectedly change course and set its sights on our planet, NASA has actionable plans to deal with it.

For example, on September 26, 2022, the space agency intentionally crashed an uncrewed spacecraft into a 525-foot (160-meter) wide asteroid. The goal was to slightly alter the space rock's trajectory—which, fortunately, was not headed toward Earth anyway [3].

Through test missions like the Double Asteroid Redirection Test (DART), NASA aims to verify whether crashing a spacecraft into an asteroid is a viable planetary defense strategy to prevent future impacts and other space threats.