Our solar system is a busy place, filled with planets, moons, and comets. It is also filled with millions of asteroids, which are large and small rocks left over from when our solar system first formed. Most of these asteroids stay far away from Earth, orbiting the Sun in a large ring called the asteroid belt, located between Mars and Jupiter. Sometimes, however, an asteroid’s path, or orbit, brings it into our part of the solar system, where it can cross paths with Earth. Scientists call these objects “Near-Earth Objects,” and it is their job to find and track them.
One of the most famous of these asteroids is named Apophis. Discovered in 2004, Apophis quickly got the world’s attention. It is a very large space rock, about 1,100 feet (or 340 meters) wide. That is as tall as a giant skyscraper, like the Eiffel Tower or the Chrysler Building. For many years, scientists were worried about Apophis. Their early calculations showed its path was uncertain, and it looked like it had a small chance of hitting Earth, first in 2029 and then perhaps in 2036. This news made Apophis one of the most-watched and most-studied asteroids in history.
The good news is that we are safe. After many years of careful observation, especially using powerful radar in 2021, scientists have confirmed that Apophis will not hit Earth. Its path is now known very, very well. It will miss us in 2029, and it will miss us for at least the next one hundred years. But this entire experience was a serious wake-up call for the world. It made scientists and governments ask a very important question. Apophis is going to miss, but what would we really do if the next big asteroid was on a direct path to hit us?
What is the Asteroid Apophis and Why Did It Worry Scientists?
Apophis, also known by its scientific number 99942, is a stony-type asteroid. This means it is made mostly of rock and metals. Scientists also believe it is not a single, solid piece of rock. Instead, they think it is a “rubble pile.” This means it is a collection of many different-sized boulders, pebbles, and dust, all held together loosely by their own weak gravity. When it was first discovered in 2004, astronomers had only a few pictures of it, making its exact path hard to predict. As they watched it, their calculations showed a small but very real possibility of an impact in 2029.
This was so concerning that Apophis briefly reached a level 4 on the “Torino Scale.” The Torino Scale is a 0-to-10 system that scientists use to rate the danger of a future asteroid impact, like the Richter scale for earthquakes. A 0 means no danger, while a 10 means a certain collision that could end civilization. No other asteroid in modern history has ever been rated above a level 1. A level 4 meant Apophis had a “merits close attention” rating, with a serious chance of causing regional devastation. This is why astronomers all over the world pointed their telescopes at it every time it came near, trying to get more data. Thankfully, every new observation, especially powerful radar scans, helped them remove the uncertainty. In 2021, they were finally able to reduce its risk all the way down to 0.
How Close Will Apophis Come to Earth in 2029?
Even though it will miss us, the Apophis flyby on April 13, 2029, will be a historic and mind-blowing event. This date, a Friday the 13th, will be when the asteroid comes incredibly close to our planet. Apophis will fly by at a distance of about 19,000 miles (or 31,000 kilometers) above the surface. To understand how close this is, you need to know where our most important satellites are. The big satellites that give us our TV signals, weather forecasts, and GPS are in “geostationary orbit,” which is much farther away, at about 22,000 miles. This means Apophis will fly between Earth and these high-orbit satellites. It is very rare for an asteroid this large to come so close.
What is even more exciting is that for a short time, Apophis will be visible to the naked eye. You will not even need a telescope. For people in Europe, Africa, and Western Asia, it will look like a star, a small point of light, moving steadily across the night sky. It will be a powerful reminder that our planet is part of a larger, active solar system. This close pass is a once-in-a-thousand-years opportunity for scientists. They will be able to study the asteroid in amazing detail, learning about its shape, its spin, and what it is made of, all without having to launch an expensive, years-long mission to meet it in deep space.
Why is the 2029 Apophis Flyby So Exciting for Scientists?
For scientists, the 2029 pass is like getting a free, close-up look at a visitor from deep space. NASA is even redirecting one of its existing spacecraft, OSIRIS-REx (which just returned a sample from another asteroid), to go meet Apophis right after its flyby. This mission will be renamed OSIRIS-APEX. The scientific opportunities are huge. First, they want to see what Apophis is made of. Understanding its materials helps us understand how the solar system formed. Second, they are very curious about its “rubble pile” structure. They want to know how these loose piles of rock and dust manage to hold themselves together.
The most interesting part, however, is what Earth’s gravity will do to Apophis as it passes by. Our planet is massive, and its gravity will pull on the asteroid very strongly. Scientists believe this gravitational pull could be strong enough to shake the asteroid, causing “asteroid-quakes” on its surface. It might even move boulders around or cause small landslides of dust and pebbles. Earth’s gravity might slightly change the asteroid’s shape or how it spins. By watching these changes happen, scientists can learn about the inside of the asteroid. This will give them vital information for the future, just in case we ever do need to stop a rubble-pile asteroid from hitting us.
What Would Happen If an Asteroid Like Apophis Actually Hit Earth?
This is the serious, hypothetical question at the heart of the Apophis story. Let’s be very clear: an Apophis-sized impact is not an “extinction-level event” like the one that killed the dinosaurs. That asteroid was enormous, estimated to be 6 to 10 miles wide. Apophis is about 1,100 feet wide. It is not big enough to threaten all human life on the planet. However, it is absolutely big enough to cause the worst natural disaster in modern human history. The level of destruction would be unimaginable, far beyond any earthquake, volcanic eruption, or hurricane we have ever seen.
If Apophis were to hit land, the results would be catastrophic. It would strike the ground at many times the speed of sound, releasing energy equivalent to over 1,000 megatons of TNT. This is many, many times more powerful than all the nuclear weapons on Earth combined. It would instantly dig a crater more than 3 miles (5 kilometers) wide and hundreds of feet deep. At the impact site, everything would be vaporized. For tens of miles in every direction, a powerful shockwave and a fireball of intense heat would flatten and burn everything. An area the size of a large state, like New Jersey or Massachusetts, would be completely destroyed. If it hit near a major city, millions would be killed instantly. Dust and debris would be thrown high into the atmosphere, which could briefly cool the climate around the world and affect farming for a season or two.
If Apophis were to hit the ocean, which is more likely since Earth is 70 percent water, the problem would not be the crater. The problem would be a megatsunami. The impact would displace a massive amount of water, creating waves hundreds of feet high that would travel across the entire ocean. These waves would move at the speed of a jetliner. When they reached coastlines, even thousands of miles away from the impact, they would wash inland for miles, destroying every coastal city in their path. The amount of water vapor and sea salt thrown into the atmosphere would also cause major, short-term changes to global weather patterns. There would be no safe place in the entire impact basin.
How Do Scientists Find and Track Dangerous Asteroids?
Because the threat is so serious, scientists around the world work every single night to find these dangerous objects. This effort is called “Planetary Defense.” The first step is finding them. This is done by special automated telescopes on Earth, like the Pan-STARRS in Hawaii and the Catalina Sky Survey in Arizona. These telescopes scan the entire sky, night after night, taking pictures. Special computer programs then look at these pictures, searching for tiny dots of light that are moving against the background of fixed stars. When they find one, it is reported to the Minor Planet Center, a global office that collects all the data.
Once a new asteroid is found, especially one that comes near Earth’s orbit, it is carefully tracked. Astronomers use telescopes all over the world to get more observations. The more they observe it, the better they can calculate its future path. For asteroids that come very close, the most powerful tool is planetary radar. By bouncing powerful radio waves off the asteroid from giant dishes, like NASA’s Goldstone Deep Space Communications Complex, they can measure its exact distance, speed, size, and shape with incredible precision. This radar data is what allowed scientists to definitively rule out an Apophis impact. The challenge is finding all of them. While we have found most of the giant, dinosaur-killer-sized asteroids, we have probably only found less than half of the asteroids in the Apophis size range.
What Is Planetary Defense and How Could We Stop an Asteroid?
Finding an asteroid is step one. Step two is knowing what to do about it. This is the “defense” part of Planetary Defense. The good news is that we are no longer helpless. We have real, tested technology that could protect us, as long as we have enough warning time. The key is that we do not need to destroy the asteroid. Blowing it up, like in movies, is actually a bad idea. It could just create a “shotgun blast” of many smaller, still-dangerous rocks that would hit Earth in multiple places. The goal is to deflect the asteroid, which means giving it a tiny push. A tiny nudge, given years or even decades in advance, is all it takes to change its path just enough so that it misses Earth completely.
We have a few proven or well-studied ways to do this. The most-tested method is the “kinetic impactor.” This is basically a high-speed game of pool in space. You slam a heavy, fast-moving robotic spacecraft directly into the asteroid. The crash itself gives the asteroid a push. In 2022, NASA proved this works with its DART (Double Asteroid Redirection Test) mission. The DART spacecraft successfully crashed into a small asteroid named Dimorphos and measurably changed its orbit. This was a huge success for humanity, proving we can move an asteroid. For a larger object like Apophis, we might need a bigger spacecraft or perhaps several of them hitting it at once.
Another method, for when we have decades of warning, is the “gravity tractor.” This sounds like science fiction, but the physics is simple. You would send a heavy spacecraft to the asteroid and just park it in orbit right next to it. The spacecraft would not even touch the asteroid. Instead, it would just fly alongside it for many years. Every object with mass has gravity, even a spacecraft. That tiny, tiny gravitational pull from the spacecraft, added up over 10 or 20 years, would be just enough to slowly and gently tug the asteroid onto a new, safe path. This is a very precise and safe method, but it requires finding the asteroid very, very early. As a last resort for a huge object with little warning, a nuclear device could be used. But even then, the plan would be to detonate it near the asteroid, not on it. The intense radiation and heat from the blast would vaporize one side of the asteroid, creating a massive, rocket-like thrust that pushes it away.
How Much Warning Time Would We Need to Stop an Asteroid?
When it comes to stopping an asteroid, the most important resource we have is not money or rockets. It is time. The more warning time we have, the easier the problem is to solve. If we find a dangerous asteroid 20, 30, or 50 years before it is set to impact, the solution is relatively simple. A single DART-style kinetic impactor or a gentle gravity tractor would have more than enough time to give it the tiny nudge it needs to miss Earth by a safe margin. The mission would be lower-cost, lower-risk, and have a very high chance of success. This is the ideal scenario, and it is why the most important part of planetary defense is finding the asteroids now.
If our warning time is shorter, the problem gets much harder. If we only have, for example, five to ten years of warning, a single small impactor might not be enough. We might need to launch a much heavier, faster spacecraft, or possibly a whole fleet of them, to hit the asteroid hard enough to move it in time. This would be a much more expensive and difficult mission. The nightmare scenario is finding a large asteroid only months before impact. At that point, a kinetic impactor would be useless; it simply would not have enough time to change the asteroid’s path. Our only option might be the last-ditch nuclear device, with all its risks. Or, if the asteroid is not too big, the only plan might be to evacuate the impact zone, which would be a global crisis. The Apophis story shows us the value of time: we found it in 2004, 25 years before its close 2029 pass. That was more than enough time to act, if we had needed to.
Conclusion
The story of the asteroid Apophis is both a relief and a powerful lesson. We are incredibly fortunate that this particular skyscraper-sized rock is going to miss us, giving us a spectacular and safe front-row seat to a rare cosmic event in 2029. But Apophis was the perfect fire drill for our planet. It showed us that these threats are real, that they are out there, and that we cannot afford to ignore them.
Because of the questions Apophis raised, our planetary defense programs are stronger than ever. We have proven with the DART mission that we are not dinosaurs; we have the technology and the ability to change our own fate. The threat of Apophis pushed us to build better telescopes, run the calculations, and test the solutions. We know we are safe from Apophis, but the work of finding the thousands of other asteroids just like it, whose paths we do not yet know, continues every single night. It really makes you think about how our view of the sky has changed, from a place of mystery to a place we must actively watch and protect, doesn’t it?
FAQs – People Also Ask
What does the name Apophis mean?
Apophis is the Greek name for an ancient Egyptian deity. This god, also known as Apep, was the spirit of chaos, darkness, and destruction. Given the asteroid’s initial threat, the discoverers chose this name because it seemed very fitting for an object that could cause such great harm.
Is Apophis a “planet killer”?
No, Apophis is not a planet killer or an extinction-level event asteroid. The asteroid that killed the dinosaurs was many miles wide. Apophis is about 1,100 feet wide, which makes it a “city killer” or a “regional devastator.” It would cause an unbelievable disaster, but it would not threaten the survival of all humanity.
Can we see Apophis from Earth in 2029?
Yes, but only from certain parts of the world. On April 13, 2029, it will be visible for a few hours to the naked eye from Europe, Africa, and western Asia. It will look like a moderately bright star moving steadily across the sky, and it will be bright enough to see even without a telescope or binoculars.
Did the DART mission target Apophis?
No, the DART mission did not target Apophis. DART was a test mission sent to a different, much smaller asteroid named Dimorphos, which was orbiting a larger asteroid, Didymos. The goal was simply to prove that the “kinetic impactor” technique worked, and it was a great success.
What is a “rubble pile” asteroid?
A rubble pile asteroid is not a single, solid piece of rock. Instead, it is a loose collection of many different-sized rocks, boulders, gravel, and dust. All these pieces are held together very weakly by their own combined gravity. Many asteroids, including Apophis, are thought to be rubble piles.
What is the Torino Scale?
The Torino Scale is a 0-to-10 rating system that scientists use to communicate the potential danger of a future asteroid or comet impact. A rating of 0 means there is no risk. A rating of 10 means a certain collision that will cause a global catastrophe. Apophis once reached level 4, the highest rating any asteroid has ever received, but it is now at 0.
What is the difference between an asteroid and a meteor?
The difference is all about location. An asteroid is a large rocky object orbiting the Sun in space. A meteor, or “shooting star,” is the streak of light we see when a small piece of rock (a meteoroid) enters Earth’s atmosphere and burns up. If any piece of it survives the fall and hits the ground, it is called a meteorite.
How many potentially hazardous asteroids are there?
Scientists have currently found over 2,000 “Potentially Hazardous Asteroids,” or PHAs. This is a label for any asteroid larger than about 460 feet (140 meters) that comes within a certain close distance of Earth’s orbit. They are tracking all of these, but they believe there are still many thousands more left to be discovered.
Could Earth’s gravity break Apophis apart in 2029?
It is possible that Earth’s gravity could affect Apophis, but it is not expected to break it apart completely. As it passes, the strong pull of Earth’s gravity (called tidal forces) might be enough to cause “asteroid-quakes” or small landslides on its surface, and it might even slightly change its spin. Scientists are very excited to watch this happen.
What is NASA’s main program for finding asteroids?
NASA’s main office for this is the Planetary Defense Coordination Office (PDCO). This office oversees all of NASA’s projects for finding, tracking, and studying Near-Earth Objects. It supports the various sky surveys that hunt for asteroids and is developing future missions, like the NEO Surveyor space telescope, to find them even faster.