The Chances of an Asteroid Hitting Earth and Humanity’s Survival Prospects

The chances of an asteroid hitting the earth are very small, or at least during our lifetimes. According to NASA, an asteroid about the size of a car hits Earth each year but always burns up in the atmosphere due to its size. Around every 2,000 years, an asteroid between 1 and 2 acres in impact surface area will hit the Earth, causing massive amounts of damage. The last time this happened is believed to have been on 30 June 1908, during something that has come to be known as the Tunguska event. Every half a million years or so, a larger one up to 5 km wide hits the planet, causing a mini version of what happened to the dinosaurs.

How Likely Is an Asteroid Impact?

Asteroids are remnants from the formation of the solar system, mostly orbiting the Sun in the asteroid belt between Mars and Jupiter. Occasionally, gravitational interactions, collisions, or other disturbances send asteroids hurtling toward Earth’s neighborhood.

The Earth is no stranger to asteroid impacts. On average, our planet is struck by an asteroid about the size of a car (roughly 2 meters across) every year, but these burn up harmlessly in the atmosphere.

Larger impacts are far less frequent:

City-Destroying Impacts: An asteroid about 25 meters in diameter (similar to the Chelyabinsk meteor that exploded over Russia in 2013) hits Earth roughly once every few decades. These can cause localized destruction.

Region-Altering Impacts: Asteroids 140 meters across, capable of devastating an area the size of a small country, strike approximately every 10,000 years.

Global Catastrophes: Impacts by asteroids 1 kilometer or more in diameter occur every 500,000 to 1 million years. These could have global consequences for climate, agriculture, and ecosystems.

Mass Extinction Events: The last known impact of a 10-kilometer asteroid occurred 66 million years ago, triggering the Cretaceous-Paleogene extinction event that wiped out the dinosaurs. Such events are extremely rare, occurring roughly once every 100 million years.

Currently, NASA tracks near-Earth objects (NEOs) that could pose a threat. As of 2024, more than 30,000 NEOs have been cataloged, and none of the largest ones are on a collision course with Earth for the foreseeable future.

Effects of Asteroid Impacts Based on Size

The destructive potential of an asteroid depends on its size, composition, speed, and angle of entry. Here’s how different-sized impacts could affect Earth and our ability to survive:

Small Asteroids (Under 50 Meters)

Asteroids smaller than 50 meters in diameter often disintegrate in the atmosphere. For example:

The Chelyabinsk meteor was about 20 meters wide. It exploded 30 kilometers above ground, generating a shockwave that damaged buildings and injured 1,500 people, but caused no direct fatalities.

Survival Likelihood: High. Small asteroids are unlikely to penetrate the atmosphere and cause significant damage.

Medium-sized asteroids (50 to 300 Meters)

Asteroids in this range can cause substantial destruction if they reach the surface or explode near populated areas.

A 140-meter asteroid could unleash energy equivalent to hundreds of nuclear bombs, obliterating a city or small country. The Tunguska event in 1908, caused by an asteroid or comet about 50 meters across, flattened 2,000 square kilometers of Siberian forest.

Survival Likelihood: Moderate to High. The damage would be localized, and global infrastructure and human populations could endure. Evacuation and disaster response could minimize casualties if detected early.

Large Asteroids (300 Meters to 1 Kilometer)

Asteroids of this size are considered global threats. A collision would cause regional devastation and significant climate effects due to the release of dust and aerosols.

A 1-kilometer asteroid striking the ocean would generate massive tsunamis, while an impact on land could eject enough debris to darken skies for years, disrupting agriculture.

Survival Likelihood: Moderate. While billions could perish from immediate effects and ensuing famine, humanity might adapt using advanced technology and global coordination.

Planet-Killers (Over 10 Kilometers)

Asteroids larger than 10 kilometers, like the one that caused the extinction of the dinosaurs, would have devastating global consequences:

The impact would release unimaginable energy, triggering earthquakes, wildfires, and ejecting massive amounts of debris into the atmosphere. A “nuclear winter” scenario would follow, with drastically reduced sunlight and temperatures causing global crop failures.

Survival Likelihood: Low. Advanced technology, such as underground bunkers and hydroponic food systems, might enable small groups of humans to survive, but large-scale civilization would collapse.

Defending Against Asteroids: Could We Prevent a Collision?

Humanity is no longer a passive victim of cosmic events. Advances in technology and space exploration have given us tools to detect and potentially deflect hazardous asteroids.

Detection and Tracking

Programs like NASA’s Planetary Defense Coordination Office (PDCO) and telescopes such as the Pan-STARRS and NEOWISE scan the skies for NEOs.

Current technology allows us to detect most asteroids larger than 140 meters with decades of warning.

Deflection Strategies

Kinetic Impactors: Spacecraft could collide with an asteroid to alter its trajectory. NASA’s DART (Double Asteroid Redirection Test) demonstrated this capability in 2022 by altering the orbit of an asteroid moonlet, Dimorphos.

Gravity Tractors: A spacecraft could fly alongside an asteroid, using its gravitational pull to nudge the asteroid off course.

Nuclear Explosions: While controversial, detonating a nuclear device near an asteroid could vaporize part of its surface, generating a thrust that changes its path.

Laser Ablation: Focused lasers could gradually vaporize asteroid material, creating a gentle push to alter its trajectory.

Global Preparedness

Despite technological advances, our ability to respond effectively depends on early detection. For large, fast-moving asteroids detected late, humanity might have no viable defense. International collaboration and investment in planetary defense are crucial.

Surviving an Impact

If an asteroid were on a collision course with Earth, the survival of humanity would depend on several factors:

Evacuation: For localized impacts, governments could evacuate areas in the asteroid’s predicted path. This requires precise prediction models and robust emergency infrastructure.

Climate Mitigation: For larger impacts, preparing for global climate effects is essential. Stockpiling food, creating artificial sunlight systems, and developing genetically modified crops could help sustain survivors.

Underground Shelters: Bunkers equipped with life-support systems could protect small populations from prolonged environmental disasters.

Space Colonization: Long-term, humanity’s best chance of survival may lie in establishing self-sustaining colonies on the Moon, Mars, or beyond, reducing dependence on Earth.

The risk of a catastrophic asteroid impact is low but not negligible. With proper investment in detection, deflection, and preparedness, humanity can significantly reduce the threat. Surviving an impact depends on the asteroid’s size and our ability to respond effectively. While small and medium-sized asteroids are unlikely to threaten humanity’s existence, larger ones require a coordinated global effort to prevent widespread devastation.

By continuing to develop planetary defense strategies and fostering international cooperation, humanity can ensure that an asteroid strike remains a fascinating topic for science fiction, not a future disaster.