The Hidden Threat: Why We Struggle to Detect Dangerous Asteroids Before They Strike

The Chelyabinsk Incident: A Wake-Up Call

On February 15, 2013, an asteroid heavier than the Eiffel Tower entered Earth's atmosphere over Chelyabinsk, Russia. Moving at an astonishing speed of 19 kilometers per second, it exploded 30 kilometers above the ground, creating a blinding flash that outshone the sun.

For a full 90 seconds, the explosion remained eerily silent, giving people just enough time to rush to their windows, curious about the strange event they had just witnessed. Then, without warning, the shockwave struck. It shattered windows, blew doors off their hinges, and sent glass shards flying into the faces of onlookers. Over 1,500 people were injured, and thousands of buildings sustained damage.

What made this event even more astonishing was that scientists had predicted an asteroid fly-by on the very same day. An asteroid named Duende, roughly the same size as the Chelyabinsk impactor, passed within 27,000 kilometers of Earth—closer than some satellites in orbit. And yet, despite their success in predicting that near miss, astronomers completely missed the asteroid that actually hit.

This was a sobering reminder of how difficult it is to detect incoming space rocks, especially smaller ones. If an asteroid that caused so much damage could slip by unnoticed, how many others might be out there, heading our way?

Why Are Asteroids So Hard to Detect?

Asteroids are the leftover building blocks of the solar system, composed of rock, metal, or loose rubble. While most remain in the asteroid belt between Mars and Jupiter, thousands have drifted into near-Earth orbits. These near-Earth objects (NEOs) pose the greatest potential threat to our planet.

Despite our advanced telescopes, tracking asteroids is a formidable challenge for several reasons:

1. They Are Small and Dark

Most asteroids don’t reflect much sunlight. Unlike the bright stars and planets, they only reflect about 15% of the light that hits them. This makes them difficult to spot, even with powerful telescopes. The smaller the asteroid, the harder it is to see—yet even small ones can be devastating. The Chelyabinsk meteor, for instance, was only about 20 meters wide—roughly the size of two school buses—but still caused significant destruction.

2. They Can Approach from the Sun’s Direction

Astronomers primarily detect asteroids by spotting them against the dark backdrop of space. But any asteroid coming from the direction of the sun is virtually invisible. The Chelyabinsk meteor came from this blind spot, giving no warning before impact. This highlights a major flaw in our asteroid detection capabilities.

3. Their Orbits Are Unpredictable

Asteroids don’t travel in perfect, unchanging paths. The gravitational pull of planets—especially giant ones like Jupiter—constantly nudges them off course. Even a tiny shift in trajectory can have massive consequences over time. Because of this dynamical chaos, our ability to predict asteroid paths beyond 100 years into the future is limited.

To date, we have cataloged over 1 million asteroids, with around 24,000 classified as near-Earth objects. However, many smaller but still dangerous asteroids remain undetected.


What If a Large Asteroid Hit Earth?

While Hollywood loves depicting asteroid impacts as world-ending events, the reality depends largely on the asteroid’s size.

Small Asteroids (Under 50 meters wide)

Asteroids smaller than 50 meters tend to explode in the atmosphere rather than hitting the ground. The Chelyabinsk event is an example of this. While these airbursts can cause injuries and damage, they do not pose an extinction-level threat.

Medium-Sized Asteroids (50 meters to 1 kilometer wide)

An asteroid in this size range could destroy an entire city or region. The Barringer Crater in Arizona, a 1.2-kilometer-wide impact site, was formed by a 50-meter-wide asteroid hitting the Earth 50,000 years ago. The impact released energy equivalent to 10 megatons of TNT—600 times more powerful than the Hiroshima bomb.

Large Asteroids (1–10 kilometers wide)

Asteroids of this size would wipe out entire countries or cause widespread destruction. If a 1-kilometer asteroid hit the Earth, it could create a blast capable of flattening an area the size of France or Germany.

Extinction-Level Asteroids (Over 10 kilometers wide)

A 10-kilometer asteroid impact, like the one that wiped out the dinosaurs 66 million years ago, would cause a global catastrophe. The impact would send debris into orbit, setting the sky ablaze as it rained down, boiling everything alive. It would also trigger massive wildfires, block sunlight for years, and cause a global climate collapse.

The good news? We’ve ruled out any extinction-level impacts in the next 100 years. However, city-destroying asteroids remain a real and unpredictable threat.

Could We Stop an Incoming Asteroid?

Right now, we have no reliable method of stopping an asteroid from hitting Earth. Several ideas have been proposed, but each has significant challenges:

1. Nuking the Asteroid

Blowing up an asteroid with nuclear weapons sounds dramatic, but it may not work. Many asteroids are rubble piles—collections of loosely held rocks. A nuclear explosion might simply scatter them, creating multiple impactors instead of one. Worse, gravity might pull them back together.

2. Pushing It with Rockets

Attaching rockets to an asteroid to push it off course is another idea. The problem? We don’t have rockets powerful enough, and keeping them attached to a spinning asteroid for years would be nearly impossible.

3. Using a Gravity Tractor

A spacecraft could park near an asteroid and use its own gravity to slowly pull the asteroid off course over many years. This method is feasible but requires decades of advance warning.

4. Wrapping It in Reflective Material

Some scientists have suggested wrapping an asteroid in aluminum foil or reflective material to alter the way it absorbs sunlight. This could subtly change its orbit over time. However, covering an asteroid in foil is easier said than done.


What Can We Do?

Since we can’t stop an asteroid on short notice, the best defense is early detection. Investing in more telescopes—especially space-based ones—will improve our ability to spot threats before they get too close. Missions like NASA’s NEO Surveyor and the Vera C. Rubin Observatory aim to find thousands of near-Earth objects that are currently undetected.

If we spot a hazardous asteroid decades in advance, small interventions—like a gravity tractor—might be enough to alter its trajectory. But without early detection, our options are grim.

The Chelyabinsk event was a warning. While large asteroid impacts are rare, they are inevitable. The only way to protect ourselves is to find them before they find us.