How Planetary Defense Could Save Earth From Asteroids

planetary defense – A meteoroid fireball over Massachusetts—followed by two sonic booms—was a reminder that Earth lives in the path of fast-moving space debris. The article lays out why a future “six-mile-wide” killer would be impossible to stop, while smaller objects—from about

In late May, residents across Massachusetts and beyond saw a brilliant flash in the sky in broad daylight. Seconds later came two sonic booms that rattled windows, shook houses, and triggered a flood of 911 calls. Some people thought it was an earthquake. Others blamed thunder, an explosion, or a military flyover.

The real culprit was out of this world. A small meteoroid—about five feet wide and as heavy as an elephant—entered Earth’s atmosphere at 42. 000 miles per hour before disintegrating dozens of miles above the ground. The midair explosion released a pressure wave equivalent to 230–300 tons of TNT. and any surviving fragments likely fell into Cape Cod Bay.

For a public already buzzing about space after the recent success of Artemis II. the incident landed as both spectacle and warning. Space isn’t empty, the article argues. It’s a celestial shooting gallery—filled not just with meteoroids. but also with larger bodies such as comets. asteroids. and other cosmic detritus.

And Earth, in that account, is in the firing line.

Earlier in May, the newly discovered asteroid 2026 JH2—estimated at 50 to 115 feet wide—missed Earth by 56,000 miles. Had it been on a collision course, it could have destroyed a major city.

That still isn’t the worst scenario the article describes. It points to the scale of catastrophe possible from much larger objects. British physicist Stephen Hawking believed a cosmic impact poses one of humanity’s greatest threats—far greater than any global pandemic or a disaster on Earth.

The core question, in that framing, isn’t whether there will be a direct hit, but when.

For the biggest threats, the article says, there may be no practical defense. A rare giant projectile many miles in diameter would leave humans powerless. Unlike the dinosaurs. people might have time to see a six-mile-wide killer asteroid approaching. but stopping or deflecting it is “out of the question.” The comparison offered is stark: trying to stop an oncoming truck by throwing ping-pong balls at it.

Even with progress in discovery—astronomers have found the vast majority of near-Earth objects (NEOs) larger than about two-thirds of a mile across—the article warns that the next enormous comet could still be found only after it has already become a danger.

So the focus shifts to objects smaller than the truly catastrophic scale: those ranging from about 100 yards to about a half a mile. The article describes them as relatively numerous, capable of causing many tens of millions of casualties.

Earth is hit by a 400-yard asteroid on average once every 100,000 years. If such a collision occurred in Europe. the article says a country like France would disappear completely from the map. and the entire continent would become an unimaginable disaster area. In theory, such impacts could be preventable—making planetary defense a goal worth pursuing.

A Dutch astrophysicist. Piet Hut of the Institute for Advanced Study in Princeton. New Jersey. is presented as one of the figures pushing the issue forward. After the 1998 Hollywood films Deep Impact and Armageddon made doomsday scenarios part of popular culture. Hut organized a workshop on how to avert an impact. A year later. in October 2002. together with a fellow astronomer and two former astronauts. he founded the B612 Foundation. a private nonprofit aimed at investigating how to deflect approaching celestial bodies.

Ten years ago, the foundation planned to launch a satellite called Sentinel to search for potentially dangerous asteroids. That project was canceled for lack of funds, but B612 remains an advocate for serious research into planetary defense techniques.

The article then moves through the broader institutional landscape. NASA has its own Planetary Defense Coordination Office. The European Space Agency (ESA) has invested in NEOShield and NEOShield-2—European Union–funded research programs that studied the most plausible methods for asteroid deflection. The U.S. National Science and Technology Council has developed its own National Near-Earth Object Preparedness Strategy. Even within the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS). there is an action team addressing the threat of cosmic impacts. The UN also has an International Asteroid Warning Network, and it has added a Space Mission Planning Advisory Group.

All of that, the article suggests, means many meetings are already underway.

How would it work if an object really threatened Earth?

The article lays out a menu of options—some dismissed as impractical, others tested, many expensive, and still others speculative.

Blowing an asteroid up with an atomic bomb is described as not a smart idea. Edward Teller—known as the father of the hydrogen bomb—proposed the concept long ago. but the article argues that the resulting fragments would keep moving through space in roughly the same direction and at the original high speed. Earth would then face not one impact, but a series of smaller ones.

A more practical solution, the piece says, would be a slight deflection: shifting an approaching object so it passes close to Earth rather than colliding. If the threat is spotted years in advance, the article says, a small nudge could be enough.

The asteroid Apophis is used as the example. For a time, it appeared as though Apophis—1,100 feet wide—could wreak havoc on Earth in 2029. But the calculations described in the article showed that a minimal change in speed of just a few micrometers per second could prevent the anticipated catastrophe. In the end. no intervention is needed because Apophis will safely fly by Earth on April 13. 2029. at a distance of about 20. 000 miles.

The article also points to an intentional deflection test closer to today. In September 2022, NASA deflected a small celestial body by using its DART (Double Asteroid Redirection Test) spacecraft. DART intentionally slammed into Dimorphos, a 525-foot-wide asteroid, successfully changing its orbit around the larger parent body Didymos.

At Lawrence Livermore National Laboratory, the HAMMER project is described as an idea on the drawing board. HAMMER stands for Hypervelocity Asteroid Mitigation Mission for Emergency Response. The concept is a celestial battering ram—10 yards long and weighing almost 9 tons—fired at high velocity at a small near-Earth object. With a 10-year warning period, the article says it could deflect a 100-yard-wide object enough to prevent an impact. For something larger, the piece suggests sending 10 or 20 HAMMERs—possibly 50 or 100.

The article acknowledges the cost, but frames it against potential human lives: if it could save 100 million lives, then cost would be secondary.

Other approaches mentioned include using a rocket motor placed on the asteroid’s surface—accelerating or decelerating the NEO by extracting or leveraging fuel. The article suggests hydrogen could be extracted from ice and oxygen from rock. It also describes a variant based on Newton’s third law: catapulting material from the NEO into space at high speed would push the asteroid in the opposite direction. like a rocket effect.

Thermodynamics enters the discussion too. One idea is heating a small area on one side of the asteroid until surface material evaporates and jets off into space. That jetting gas would propel the asteroid a tiny bit in the other direction. The article ties the concept to a simple everyday image—how a magnifying glass can set a piece of paper or a shoelace on fire—then expands it to focusing sunlight on an asteroid using a large swarm of satellites equipped with gigantic lenses.

Laser cannons are also listed as an option, alongside a nuclear explosion at a short distance.

The piece describes variations that tweak how sunlight interacts with an asteroid. Wrapping an approaching NEO in thin. reflective foil could strengthen or weaken the Yarkovsky effect—the tiny push sunlight exerts on a rotating asteroid. Another way to reach a similar result is described as giving the asteroid a “once-over” with a can of spray paint.

Finally, the article returns to what it calls a least invasive option: the gravity tractor. Developed by former astronaut Ed Lu. a cofounder of the B612 Foundation. and his colleague Stan Love. the gravity tractor concept uses a large. heavy space probe that would fly alongside the near-Earth object for an extended period—years to decades—and slowly drag it away from its collision course. The article notes the probe would need to keep its rocket engine running the whole time; otherwise. it would be pulled in by the object’s gravity. With enough time and careful maneuvering, the goal would be to pull a killer asteroid into a safe orbit.

For all the technical imagination, the article insists this is not just a science problem. It also turns to politics.

Planetary defense strategies may sound fantastical, the piece says, and that’s before confronting political obstacles. The example offered is immediate and personal: suppose a relatively small near-Earth object is speeding toward Dallas—whose population is over a million—threatening to wipe the city off the map. Would Russia and China be willing to help pay for a rescue mission?. Would Americans have money to spare to preserve Chengdu?. Would people in Europe care about Zimbabwe’s possible fate?.

Carl Sagan is cited in the article for a further complication. If a country can deflect a small asteroid so it passes close to Earth. the same technology could potentially be used to bring the asteroid down on an enemy. In that scenario, planetary defense could become a celestial version of the Cold War—or worse.

The article places those questions on the agenda of the UN special committee dealing with the threat of cosmic impacts.

For the moment, it says, any agreement is far off. Still, the article lands on urgency. If something is in the firing line, the response has to be to protect and defend as best you can—identifying danger, studying conceivable countermeasures, and being ready to act when necessary.

It closes with a familiar pressure: as with the coronavirus pandemic and the climate crisis, the urgency is likely to sink in only when the need arises. The hope is that it won’t be too late by then.

This article was originally published by The MIT Reader Press.

asteroid meteoroid planetary defense NEO DART Apophis HAMMER B612 Foundation gravity tractor Yarkovsky effect NASA ESA COPUOS