Apophis is not a planet killer. At roughly 375 meters wide, it falls well below the size threshold for an asteroid capable of causing global devastation. A true “planet killer” would need to be at least 1 to 2 kilometers in diameter to trigger worldwide effects like prolonged climate disruption and mass extinction. Apophis is less than a quarter of that size.
How Big Apophis Actually Is
Apophis is an irregular, elongated rock about 375 meters across, with a mass of approximately 20 million tons. That sounds enormous, but context matters. The asteroid that carved out the Chicxulub crater and wiped out the dinosaurs 65 million years ago was roughly 10 kilometers (6 miles) wide, with about ten thousand times the mass of Apophis. Putting those two objects side by side makes clear just how different the scales are.
NASA classifies rocky objects smaller than 1 kilometer as capable of causing local or regional damage if they hit Earth, not global catastrophe. At 375 meters, Apophis sits firmly in that regional-damage category.
What an Apophis Impact Would Actually Do
If Apophis did strike Earth, it would not be harmless. The Planetary Society estimates the energy released would exceed 1,000 megatons of TNT, equivalent to tens or even hundreds of nuclear weapons detonating at once. That would devastate a large area, potentially an entire region or small country, and could trigger secondary effects like tsunamis if it hit an ocean.
But it would not block out the sun, trigger a global winter, or cause mass extinction. Those outcomes require impacts orders of magnitude more powerful. Apophis would be a catastrophic regional event, not an existential one for the planet.
The 2029 Flyby
On April 13, 2029, Apophis will pass within about 20,000 miles (32,000 kilometers) of Earth’s surface. That’s closer than the satellites orbiting in geostationary orbit, and close enough that people in parts of Europe, Africa, and Asia will be able to see the asteroid with the naked eye as it crosses the sky. No telescope needed.
This kind of close approach is extraordinarily rare for an asteroid this size. Scientists are treating it as a once-in-a-lifetime observation opportunity. NASA’s OSIRIS-APEX spacecraft, a follow-on to the mission that successfully collected samples from asteroid Bennu, will rendezvous with Apophis to study how Earth’s gravity physically alters the asteroid during the flyby. The spacecraft will eventually dip close to Apophis and fire its engines to kick up surface material, giving researchers a look at the rocky composition just below the surface.
Is There Any Risk of Impact?
No, not for the foreseeable future. When Apophis was first discovered in 2004, early calculations suggested a worrying chance of impact in 2029 or 2068. As astronomers gathered more data, that probability shrank steadily. The turning point came in March 2021, when radar observations from NASA’s Goldstone Deep Space Communications Complex tracked Apophis with extreme precision, pinning down its distance to within about 150 meters even though the asteroid was 10.6 million miles away.
Those observations collapsed the uncertainty in Apophis’s orbit from hundreds of kilometers down to just a handful. NASA formally removed Apophis from its Sentry Risk Table, the official list of objects that pose potential impact threats. The agency is confident there is no risk of Apophis hitting Earth for at least the next 100 years.
How “Planet Killer” Size Is Defined
The term “planet killer” gets used loosely, but in planetary science it refers to an asteroid large enough to cause global-scale effects: widespread fires, enough dust and debris to block sunlight for months or years, crop failures across continents, and potential mass extinction. NASA places that threshold at roughly 1 to 2 kilometers in diameter. Objects in that range carry enough kinetic energy to affect the entire planet’s climate, not just the region around the impact site.
Apophis, at 375 meters, is about one-third to one-fifth of that minimum. It’s large enough to be classified as a “potentially hazardous asteroid” based on its size and orbital proximity to Earth, but “potentially hazardous” is a technical tracking designation. It doesn’t mean the object is on a collision course or that it poses a civilization-ending threat. The good news is that NASA estimates it has identified more than 95% of near-Earth asteroids 1 kilometer and larger, and none currently pose an impact risk.