The following essay is reprinted with permission from The MIT Reader Press. Read the original story here.
In late May, during daylight hours, people across Massachusetts and nearby areas witnessed a brilliant flash in the sky, followed by two sonic booms that shook windows and houses, leading to a surge of 911 calls. Some thought it was an earthquake, while others suspected thunder, an explosion, or a military exercise.
The real cause of the disturbance was from beyond Earth—a small meteoroid, roughly five feet in diameter and weighing as much as an elephant, that entered the atmosphere at an incredible speed of 42,000 miles per hour before breaking apart high above the ground. This midair explosion generated a pressure wave comparable to 230–300 tons of TNT, and any remnants likely ended up in Cape Cod Bay.
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This event quickly captivated an American audience already more intrigued by space than usual, thanks to the recent success of Artemis II. However, it also served as a vivid reminder that space is not as empty or harmless as it might appear. Instead, our solar system is like a cosmic shooting gallery filled with flying objects—not just meteoroids, but larger entities like comets, asteroids, and other celestial debris—with Earth directly in their path. Earlier in May, for example, the newly discovered asteroid 2026 JH2, which measures between 50 and 115 feet wide, narrowly missed Earth by just 56,000 miles. Had it been on a collision course, it could have easily devastated a large city.
Yet, this isn’t the worst-case scenario for humanity. Some cosmic giants are much larger than JH2—capable of destroying entire countries or even continents. According to British physicist Stephen Hawking, a cosmic impact is one of the greatest threats to humanity, surpassing any global pandemic or natural disaster on Earth. The question is not if we will be directly hit, but when.
Regrettably, humans would be helpless against a rare, massive projectile several miles wide. Unlike the dinosaurs, we might see a six-mile-wide killer asteroid approaching, similar to the one that struck Earth 66 million years ago. However, stopping or deflecting it is impossible, akin to trying to halt a speeding truck by throwing ping-pong balls at it. While we have identified most near-Earth objects (NEOs) larger than about two-thirds of a mile and confirmed none are on a collision path with Earth, astronomers could unexpectedly discover a huge comet heading towards Earth in a few years. Once again, we would be unable to stop it.
If we do aim to shield ourselves from cosmic impacts, we need to concentrate on medium-sized objects, from approximately 100 yards to half a mile. These are quite numerous and could easily result in tens of millions of casualties. On average, Earth encounters a 400-yard asteroid every 100,000 years. If such a collision happened in Europe, a nation like France could be wiped out, and the entire continent would face catastrophic devastation. This type of impact is theoretically avoidable, so it would be irrational not to investigate potential solutions.
Dutch astrophysicist Piet Hut from the Institute for Advanced Study in Princeton, New Jersey, shared this perspective. A few years after the 1998 Hollywood movies Deep Impact and Armageddon introduced the public to impact scenarios, Hut organized a workshop to explore ways to prevent such doomsdays. A year later, in October 2002, with the help of a fellow astronomer and two astronauts, he established the B612 Foundation—a private nonprofit aimed at figuring out how to deflect incoming celestial bodies.
A decade ago, the foundation had grand plans to launch a satellite called Sentinel to search for potentially dangerous asteroids. Although the project was canceled due to insufficient funds, the B612 Foundation remains a leading proponent of serious research into planetary defense strategies.
Meanwhile, government agencies like NASA and the European Space Agency (ESA) aren’t inactive.
NASA has its Planetary Defense Coordination Office, while ESA has funded NEOShield and NEOShield-2, European Union projects that examined feasible methods for asteroid deflection. The U.S. National Science and Technology Council has crafted its National Near-Earth Object Preparedness Strategy, and within the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS), a team is working on addressing cosmic impact threats. Additionally, the UN has established a Space Mission Planning Advisory Group alongside its International Asteroid Warning Network.
Unsurprisingly, numerous meetings are currently underway to discuss how to shield humanity from cosmic threats.
How will we protect Earth?
In terms of defending Earth from a catastrophic collision, several ideas are being considered, ranging from effective to poor to very poor.
For instance, blowing up an asteroid with a nuclear bomb, as depicted in “Armageddon,” is not a wise approach. Edward Teller, recognized as “the father of the hydrogen bomb,” suggested this long ago, but it would be ineffective. The resulting fragments would continue moving through the solar system in nearly the same direction and at their original high speed. Consequently, Earth would face not one major impact but a series of smaller ones, with all the associated repercussions.
A more feasible solution would be to slightly deflect the incoming celestial body, allowing it to pass near Earth instead of hitting it. Especially if the impact can be predicted years in advance, a minor nudge could avert disaster. When astronomers discovered the 1,100-foot-wide near-Earth object Apophis, which initially seemed like it might cause chaos on Earth in 2029, they determined that a slight speed change of just a few micrometers per second could prevent the anticipated catastrophe. Fortunately, with Apophis, there’s no need for intervention: The asteroid will safely pass Earth on April 13, 2029, around 20,000 miles away.
Nevertheless, NASA recently achieved its first successful intentional asteroid deflection: In September 2022, the DART (Double Asteroid Redirection Test) spacecraft intentionally collided with the 525-foot-wide asteroid Dimorphos, successfully altering its orbit around its larger parent body Didymos.
Meanwhile, the HAMMER project is under consideration at Lawrence Livermore National Laboratory. HAMMER (Hypervelocity Asteroid Mitigation Mission for Emergency Response) is a celestial battering ram, 10 yards long and weighing nearly 9 tons, designed to strike a small near-Earth object at high speed. With a decade of warning, it could deflect a 100-yard-wide object enough to prevent an impact. If a larger object is approaching Earth, multiple HAMMERs could be deployed. Though costly, saving 100 million lives makes the expense a secondary concern.
Interestingly, there’s a more economical way to nudge a small asteroid off its original path: simply place a giant rocket motor on its surface. If a small rocket motor can launch a spacecraft, a larger one should be capable of adjusting a NEO’s speed slightly. The raw materials for rocket fuel could be sourced from the asteroid itself: Hydrogen can be obtained from ice, and oxygen from rock. Alternatively, instead of using a rocket motor, material could be catapulted from the NEO into space at high speed, creating a rocket effect in the opposite direction, courtesy of Newton’s third law.
Thermodynamics might also offer solutions. For example, heating a small area on one side of the asteroid until the surface material vaporizes and escapes into space would have the same effect as a rocket engine: Gas is expelled in one direction, propelling the asteroid a bit in the other direction. Just as a magnifying glass can ignite paper or a shoelace, sunlight can be focused on the surface of an asteroid using a large array of satellites with massive lenses. A fleet of laser cannons is another option, as is a nuclear detonation at a short distance from the celestial body. Another idea is to cover an incoming NEO in thin, reflective foil, either enhancing or diminishing the Yarkovsky effect (the tiny “push” sunlight exerts on a rotating asteroid). Spraying it with paint is yet another way to achieve the same outcome.
Lastly, a less invasive method could involve a gravity tractor, a concept developed by former astronaut Ed Lu (cofounder of the B612 Foundation) and his colleague Stan Love. This device, potentially a large, heavy space probe, would travel alongside the near-Earth object for an extended time (years to decades) and gradually pull it off its collision course. The probe’s rocket engine would need to remain active continuously; otherwise, it would be drawn in by the celestial body’s gravity. With careful maneuvering and sufficient time, a killer asteroid could be redirected into a safe orbit.
It’s not too late
Admittedly, these planetary defense strategies may sound somewhat fantastical. Moreover, the political complexities surrounding planetary defense are substantial.
Imagine a small near-Earth object speeding towards our planet, threatening to erase Dallas, with its population of over a million, from the map. Would Russia and China be willing to finance a “rescue mission”? Would Americans be willing to spend money to save Chengdu? Do Europeans care about the possible fate of Zimbabwe? American astronomer Carl Sagan foresaw another issue: If a nation can deflect a small asteroid to narrowly miss Earth, the same technology could also be used to direct the asteroid toward an enemy. Consequently, the idealistic idea of planetary defense could turn into a celestial version of the Cold War—or worse.
These are precisely the types of challenges on the agenda for the UN special committee addressing cosmic impact threats.
At present, any consensus is a distant goal. Nonetheless, action is necessary. If you are in the danger zone, you must protect and defend yourself as best as you can. We need to identify the threat, explore all potential countermeasures, and be prepared to act if required. As with the fights against the coronavirus pandemic and climate change, the urgency of the situation will likely be recognized only when the need is imminent. Hopefully, it won’t be too late by then.
This article was originally published by The MIT Reader Press. Read the original story here.
