Buzz
Finally, 2020 is behind us, and with the rollout of COVID vaccines, 2021 promises to bring more than just a chance to shake our heads at Tiger King. With the murder hornets hibernating, wildfire season wrapped up, Meth-gators in rehab, and toilet paper back on the shelves, we might actually catch a break from world-shaking events. Not so fast though. Just in time for spring, a colossal asteroid, roughly the size of the Golden Gate Bridge, is planning a close flyby, reminding us that destiny still has us in its grip.
10. Asteroid 2001 FO32
On March 21, an asteroid with an estimated diameter of one mile (1.7 km) will come within 1.3 million miles (2 million km) of Earth—about five times the distance from us to the moon (also known as Lunar Distance or LD). At nearly three times the height of the Eiffel Tower, Asteroid 2001 FO32 is larger than 97% of the asteroids currently known in our solar system. A collision with such a massive asteroid would cause a global catastrophe.
As if that weren’t alarming enough, Asteroid 2001 FO32 belongs to the Apollo-class of asteroids, meaning its orbit crosses Earth’s orbit twice during its own 810-day cycle, raising a slight risk of a collision every 2.2 Earth years. NASA considers Apollo-class asteroids to be among the most dangerous and has labeled Asteroid 2001 FO32 as a Potentially Hazardous Asteroid (PHA).
Asteroid 2001 FO32 isn’t the only space rock speeding past Earth this year, nor is it the closest. In fact, just in January, nine asteroids came closer to Earth than the Moon. Two of them were discovered only after they had already passed by.
9. What Would an Impact Look Like?
Although the odds of Asteroid 2001 FO32 hitting Earth are extremely low, what would happen if it did? The outcome depends on multiple factors such as the asteroid's size, composition, speed, impact angle, and where it strikes—whether on land or water. Since we don’t know its composition, we’ll assume it’s a common porous rock with a typical density of 1500 kg per meter (11,000 lbs/ft). The asteroid is moving at 21 miles per second (34 km/s), which is faster than most. Typically, impacts occur at a 45-degree angle as it enters the atmosphere, and for this example, we’ll say it strikes Europe—specifically Berlin—with a sedimentary rock crust.
The initial crater would measure 10 miles (16.4 km) wide and 3.6 miles (5.8 km) deep. But soon after, the ground surrounding the crater would collapse, expanding the diameter to 15 miles (23.8 km). Essentially, all of Berlin would be reduced to a massive hole. The resulting explosion—447,000 megatons, or about 30 million times the power of the Hiroshima blast—would send an air shockwave moving faster than the speed of sound, flipping cars and toppling steel buildings across Germany. This shockwave would also devastate wood-framed buildings as far east as Lviv, Ukraine, north to Stockholm, Sweden, south to Venice, Italy, and west to Paris, France. Following this, a fireball made of searing hot vapor would spread across Germany, igniting trees, grass, and clothing.
Almost everyone in Western Europe would experience vibrations similar to the passing of a truck. Earthquakes and landslides would occur across the region. Even worse, the impact would send up enough debris—called ejecta—to block out the sun globally for weeks, creating darkness darker than the heaviest cloud cover. Worldwide temperatures would plummet by 46 degrees Fahrenheit (8 degrees Celsius), canceling summer for that year. This would lead to global crop failures and, ultimately, famine. Some plant species would even become extinct regionally, and acid rain would pour down over Western Europe for months.
A more plausible scenario involves the asteroid striking one of Earth’s oceans, such as the Atlantic. The impact would create a massive void at least 11 miles (18 km) across, reaching all the way to the ocean floor, about 3 to 4 miles deep. As water rushes in to fill the gap, it would trigger a series of tsunamis radiating outward. Contrary to what movies suggest, there wouldn’t be just one colossal tsunami, but multiple waves occurring 3 to 4 minutes apart. The first waves might be small, but subsequent ones could rise to 400 feet or more. Worse still, the explosion would vaporize seawater, releasing chemicals like bromide and chloride into the atmosphere, damaging the ozone layer and leaving humans vulnerable to the sun’s harmful UV radiation. People might need to stay indoors during the day to avoid the sun’s assault.
8. Near-Earth Objects
Asteroid 2001 FO32 is far from being a lone occurrence. We’ve learned that space rocks are constantly zipping through our solar system. Take 1998, for instance. In March of that year, the scientific community released a report based on inaccurate and unverified data suggesting that Asteroid 1997 XF11 might collide with Earth in October 2028. If true, this half-mile-wide (almost 1 km) asteroid would have spelled devastation for the planet. The media quickly picked up on the report, and chaos ensued as they warned humanity of an impending doom. However, experts swiftly reassured everyone that the chances of a collision were virtually nonexistent. That summer, two major films—Deep Impact and Armageddon—brought asteroid disaster scenarios to the big screen.
In response to the scare, U.S. Congress turned to NASA that year, tasking them with tracking and cataloging Near-Earth Objects (NEOs)—comets and asteroids that come within 30 million miles (50 million km) of Earth, or about 126 times the distance from the Earth to the moon. Thus, the Near-Earth Objects Observation Program was born, which later became the Center for Near-Earth Objects Studies (CNEOS). As of October 2020, with the help of global agencies, observatories, and tracking stations, the program has identified 888 NEOs the size of Asteroid 2001 FO32 or larger. This represents around 96 percent of the estimated NEO asteroids of that size in our solar system.
Unfortunately, many smaller NEOs, which are harder to detect, remain largely untracked. Only about 20 to 30 percent of the thousands of potentially regionally-catastrophic NEOs—those about the size of a football field or larger—have been found and monitored. These asteroids, with explosions powerful enough to be measured in gigatons, would flatten entire cities and could kill millions. The bottom line is that we still don’t know the exact location of most of these dangerous space objects in our solar system.
NASA identified certain NEO asteroids that pose a particular threat—those measuring at least 140 meters in diameter and passing within a mere 5 million miles (8 million km) of Earth, roughly 21 lunar distances (LDs). These are classified as Potentially Hazardous Asteroids (PHAs). As of January 2021, 2,160 PHAs have been detected, representing about 9 percent of the 25,000 NEOs known to exist. The majority of these are Apollo-class asteroids. Around 150, or 7 percent, of these PHAs are capable of causing global devastation, similar to the effects of Asteroid 2001 FO32.
7. The Problem With the Number of Asteroids
While we have successfully tracked and detected large asteroids like 2001 FO32, smaller asteroids remain largely unmonitored. A key challenge is the sheer number of these objects. NASA estimates that over a million asteroids have been observed, yet this is only a tiny fraction of the countless others in our solar system. Most of these asteroids follow an orbit around the sun similar to the planets' path, with many clustered in the Asteroid Belt between Mars and Jupiter. The truly massive asteroids reside here, including 16 with diameters exceeding 150 miles (240 km), such as Ceres (580 miles or 940 km), Vesta (326 miles or 525 km), and Pallas (318 miles or 512 km).
NASA reports that approximately 100 tons of dust and sand-sized pebbles burn up in Earth’s atmosphere every day. From 1994 to 2013, NASA recorded 556 separate incidents where asteroids—also referred to as meteors—ranging from 3 feet (1 meter) to 60 feet (30 meters) in size entered our atmosphere and were observed by humans as fiery streaks across the sky. This averages out to about 28 fireballs annually, and each one was completely undetected before its fiery end.
However, the number of undetected asteroid and meteor impacts is far higher. Humans only occupy around 0.44% of Earth’s land area, or about 0.13% of the planet's total surface. Experts estimate that as many as 17 asteroids or meteors per day have the size and composition necessary to survive their passage through the atmosphere and land on Earth's surface. Most of these objects land in the ocean or in remote, uninhabited areas. This equates to roughly 6,100 asteroid or meteor impacts annually, and almost all of them go unnoticed by NASA and the hundreds of telescopes scanning the sky. Occasionally, these unseen impacts can prove to be devastating.
6. The Tunguska Event
On the morning of June 30, 1908, seismographs across the globe recorded a seismic disturbance that, in some regions, reached 5.0 on the Richter Scale. Windows shattered throughout Europe. For days afterward, much of Europe and Asia experienced a night sky as bright as daylight. Observatories reported a noticeable increase in atmospheric dust, which obscured the stars. However, the cause of this strange event remained unknown.
It took nearly two decades before Russian mineralogist Leonid Kulik uncovered the source of the event: a remote region in Siberia, near the Podkamennaya Tunguska River, had been completely leveled. Around 80 million trees and an area of 830 square miles (2,100 sq km) of forest were obliterated. However, no impact crater was found, and meteor debris was minimal. The most widely accepted theory is that a small asteroid or comet, between 150 to 300 feet (50 to 100 m) in size, entered Earth’s atmosphere and detonated 6 to 10 miles (10 to 15 km) above the ground, unleashing a blast 185 times more powerful than the Hiroshima bomb and a fireball 164 to 328 feet (50 to 100 m) wide.
In short, an asteroid or comet at least one-tenth the size of Asteroid 2001 FO32 flattened an area comparable to the size of Tokyo’s city limits. A review of observatories worldwide reveals that more than 100 were operational by 1908, and it’s presumed their telescopes were aimed skyward on that fateful June morning. Yet, not a single observatory reported an incoming rock set to collide with Earth.
5. The Problem with Small Asteroid Detection
We shouldn’t be too critical of the observers who were scanning the skies in June of 1908. It would actually take an entire century for humans to successfully detect an asteroid on a collision course with Earth and predict its exact impact location. That asteroid was named 2008 TC, and it was spotted only 20 hours before its arrival by the Mt. Lemmon Observatory near Tucson, Arizona.
On October 6, 2008, Mt. Lemmon notified the Minor Planet Center (MPC) at Cambridge, who then confirmed whether this asteroid had been previously discovered or was entirely new. After this, they calculated the preliminary orbit of Asteroid 2008 TC, determining that it would strike Earth the very next day. MPC promptly alerted NASA/JPL’s NEO Observation Program. While NASA raised alarms globally, JPL pinpointed the asteroid’s entry location over the Nubian Desert in Sudan. Around 26 observatories around the globe focused on this incoming object and concluded that it was about 2-5 meters across, predicting that it would detonate 23 miles (37 km) above the ground. Despite entering the atmosphere a tenth of a second later than anticipated, the 1 kiloton explosion occurred exactly on time at the predicted latitude and longitude.
But what if Mt. Lemmon had been unavailable? The scientific community was shaken last November by the collapse of the Arecibo Observatory in Puerto Rico, one of the largest single-dish telescopes in the world. This facility, active for 50 years, played a key role in protecting us from asteroid impacts, and its loss will be difficult to replace. What if Mt. Lemmon had been focused on a different part of the sky that day? Or if weather conditions had obstructed its view? One limitation of ground-based observatories is their reliance on clear skies. What if Asteroid 2008 TC had approached Earth while Tucson was on the day-side or during a cloudy night? This could explain why asteroid detection hasn't significantly improved since 2008.
The U.S. government has installed infrasound sensors worldwide designed to detect nuclear explosions. These sensors also record asteroid impacts, though they don’t capture those that land in water. In 2008, when Asteroid 2008 TC impacted, 34 other asteroid strikes went unnoticed. Our next detection success came in 2014 when Asteroid 2014 AA hit the Atlantic Ocean. That year, 33 land impacts went undetected. Another success followed in 2018 when 2018 LA impacted Botswana, Africa. However, that year, 38 asteroid impacts occurred without detection. Over 11 years, from 2008 to 2018, only 3 out of 367 impacts were detected—yielding a detection rate of less than 1%.
4. The Problem of Seeing Asteroids
Asteroids reflect sunlight, and when observed against the backdrop of space, they resemble stars (known as chalk albedo). But once they start moving, their appearance changes. Smaller asteroids reflect less sunlight (known as charcoal albedo), making them harder to detect from afar. For a small asteroid to be visible, it must be very close to Earth. We've already discussed the limitations of ground-based telescopes, which can only observe on clear nights. Additionally, most observatories are located in the Northern Hemisphere, where most of the world's landmass is situated. This leaves the Southern Hemisphere under-observed, but it also means that the Northern Hemisphere's observatories share the sky with 90% of the Earth's population, whose pollution significantly decreases the likelihood of spotting an approaching asteroid.
Space-based telescopes like Hubble have the advantage of being able to observe the sky around the clock, unaffected by pollution or clouds. However, they still struggle with detecting smaller asteroids. To address this, both land-based and space-based telescopes are now utilizing infrared technology to detect the heat emitted by asteroids as they absorb sunlight. The downside is that when an asteroid passes between Earth and the Sun, infrared technology has difficulty distinguishing the asteroid’s heat from the Sun’s heat signature. This challenge was dramatically highlighted when an asteroid exploded over Chelyabinsk, Russia in 2013.
3. The Problem of Stopping or Diverting an Asteroid
Experts have proposed several methods to save our planet from an asteroid hurtling towards us, most of which begin with sending a spacecraft to intercept the asteroid and end with altering its path. One idea is to use the spacecraft’s own gravity (since everything with mass exerts gravity) to gently nudge the asteroid off course. Another option is to attach to the asteroid like a tugboat and push it away from Earth. Alternatively, the spacecraft could attach a mass driver to the asteroid, which would shoot debris into space, using Newton's Law of Action and Reaction to push the asteroid in the opposite direction. Another idea is to heat the asteroid's surface with solar mirrors or lasers, creating jets of steam that push the rock off course. Lastly, one could consider detonating a nuclear bomb, though this is considered the least likely to succeed. It would be more effective to detonate the nuke near the asteroid, using the blast and heat to change its trajectory.
NASA and the European Space Agency (ESA) are developing two versions of a technology known as a kinetic impactor. This concept stems from the 2005 Deep Impact mission (unrelated to the movie), where a spacecraft rendezvoused with the comet Tempel 1. The spacecraft then deployed a kinetic impactor to collide with the comet, revealing what lay beneath its surface. The unplanned outcome of this mission was that it slightly altered Tempel 1’s trajectory.
This July, NASA will launch the Double Asteroid Redirection Test (DART). Fourteen months later, DART will collide with the small moonlet that orbits the NEO Didymos asteroid, traveling at 1.5 miles per second (6.6 km/s). Some asteroids, known as binary asteroids, even have moons. About one-sixth of all Near-Earth Objects (NEOs) are binary or multiple-body systems. The impact will slightly alter the moonlet’s speed, but just enough for Earth’s telescopes to confirm that a kinetic impactor is a viable method. A similar mission, the ESA’s Don Quijote (named after Don Quixote’s battle with windmills), was designed to involve two spacecraft: Sancho and Hidalgo. Sancho would have been launched first to survey the target asteroid and identify the ideal impact location. It would then send the coordinates to Hidalgo, which would carry out the impact. Unfortunately, Don Quijote is still in development.
While DART and Don Quijote are built upon existing technology, making them feasible for near-future missions, other proposed methods are still in the conceptual phase. Even if developed, these solutions would require months, if not years or even decades, to be launched into space. This means we would need ample warning for these methods to succeed. But, as we've discussed, we may not receive any warning—significant or otherwise.
2. The Problem With Predicting Impacts
If you’re finding comfort in expert statements like “Asteroids similar to the one that wiped out the dinosaurs 66 million years ago strike Earth only once every 100 million years,” be prepared for disappointment. These figures are merely averages. It’s like driving down the road, passing a fatal car accident, and thinking you’re safe for the next 16 minutes simply because such accidents occur every 16 minutes. That’s obviously not true, especially if you’re distracted while speeding at 70 miles per hour. The next major asteroid could strike Earth in an hour, a month, or even in 150 million years.
Let’s break down these averages a bit more. Experts estimate the asteroid that caused the extinction of the dinosaurs was about 30 miles (10 km) wide and strikes Earth every 100 million years on average. A 15-mile (5 km) asteroid hits every 30 million years, while a 3-mile (1 km) rock like Asteroid 2001 FO32 impacts Earth every 700,000 years. A 150-foot (50 m) asteroid, like the one that flattened Tunguska, visits every 2,000 years. Asteroids around the size of the Chelyabinsk meteor (65 feet or 20 m) appear roughly every two centuries, and those around 16 feet (5 meters) pass by every two years. However, with the exception of Tunguska and Chelyabinsk, we have no definitive knowledge of when the last large asteroid came through. We can't be sure if we’re overdue. Worse, the sample size behind these averages is, at best, a mere one. It’s hard to have faith in averages with such a small sample.
The probability of a specific asteroid colliding with Earth is based on a series of observations and orbital calculations over time. The more observations made, the more accurate the risk assessment. For example, the small asteroid 2017 WT28, measuring just 26 feet (8 m), has a 1% chance of hitting Earth in November 2104. This prediction comes from 28 observations and orbital calculations gathered over 19 days. Similarly, the NEO asteroid 2010 WC9, discovered in 2010 but lost the same day due to its fading brightness, reappeared unexpectedly in May 2018, passing within half the distance to the Moon (0.5 LD). There are nearly 1,000 NEOs that were briefly tracked before vanishing. Over 130,000 asteroids, meanwhile, were never observed long enough to be classified or assessed for any potential risk. While most of these “lost” asteroids are small, dozens exceed 1,300 feet (400 m) in size.
A further complication in asteroid predictions arises from the assumption that their orbits remain unchanged. Take, for example, Asteroid 4179 Toutatis—a massive 1.5-mile (2.5 km) asteroid that passed just 4 lunar distances (LD) from Earth in 2004, the closest any asteroid of that size has come in this century. However, Toutatis follows an extraordinarily complex and erratic orbit, influenced by the gravitational pull of both Earth and Jupiter. Due to its chaotic trajectory, experts cannot predict its potential danger to Earth beyond a few centuries.
1. The Chelyabinsk Meteor
On February 15, 2013, astronomers were eagerly preparing their telescopes for the close flyby of Asteroid 2012 DA14. This 150-foot (45 m) rock was set to pass so closely by Earth that it would be far nearer than the communication satellites in geosynchronous orbit. The world was so captivated by this event that, unfortunately, many telescopes were pointed in the wrong direction that day.
Early that morning, reports emerged of a different asteroid, about 65 feet (20 m) across, with a mass greater than that of the Eiffel Tower, exploding 14 miles above Chelyabinsk, a city in Russia's southern Urals. The explosion was estimated at 500 kilotons—20 to 30 times more powerful than the Hiroshima bomb—and was 30 times brighter than the Sun. The resulting shockwave shattered windows across 200 square miles (518 sq/km), and people were knocked off their feet. Of the 1,500 injured, at least one person suffered facial burns from radiation. Remarkably, there were no fatalities.
As the first confirmed asteroid impact in history to result in injury (unlike the Tunkuska Event, where no injuries were reported), the world was left shaken, especially since the event took everyone completely by surprise. Despite this asteroid being 4 to 10 times larger than the 2008 TC asteroid, experts argued it was too small to have been detected. They further explained that the asteroid approached from the East, with the Sun behind it, making it nearly impossible to spot either visually or by infrared methods.
