Whenever Apophis makes headlines, someone asks: is this another dinosaur killer? It is not, and the gap between the two is far bigger than most people expect. Here is a side-by-side look.
About 66 million years ago, an object roughly 10 kilometers (6 miles) wide struck what is now Mexico's Yucatán Peninsula. It left the Chicxulub crater, about 180 km across, and triggered a global catastrophe. Dust and soot blocked sunlight, temperatures collapsed, and about three quarters of all species went extinct, including all non-bird dinosaurs.
Apophis is about 340 meters (1,100 ft) across, around thirty times narrower than Chicxulub. Because volume, and therefore mass, grows with the cube of the diameter, Apophis has roughly tens of thousands of times less mass than the dinosaur impactor. Estimates of impact energy vary with speed and density, but it would be several orders of magnitude lower.
| Chicxulub impactor | Apophis | |
|---|---|---|
| Size | about 10 km | about 340 m |
| Date | about 66 million years ago | April 13, 2029 |
| Outcome | Impact, mass extinction | Safe flyby, about 32,000 km |
An impact by a 300-meter-class asteroid would be a regional catastrophe, not a global extinction event. It would devastate an area hundreds of kilometers wide on land, or produce a dangerous tsunami in the sea. That is serious, but it is a very different scale from Chicxulub. And again: Apophis is not going to hit.
Dinosaur-class impacts, with objects of 10 km or more, are extremely rare, on the order of once in many tens of millions of years. Astronomers believe they have found almost all near-Earth asteroids larger than 1 km, and none is on a collision course in the foreseeable future. The objects that remain hard to find are the smaller ones, which is where surveys are focusing now.
The evidence is not a legend. In 1980, a team led by Luis and Walter Alvarez reported a thin layer of clay in rocks from around the world, dating to the end of the Cretaceous, containing unusually high amounts of iridium, an element that is rare in Earth's crust but more common in asteroids. Later, geologists connected this layer to a huge buried crater beneath the Yucatan Peninsula. In 2016, an international drilling expedition recovered rock cores from the crater's ring of peaks, and they showed the signs of an enormous, sudden impact. Together, these findings make the Chicxulub event one of the best-supported explanations for the mass extinction.
Tunguska, 1908. A space rock, probably only tens of meters wide, exploded in the air above a remote part of Siberia. It flattened trees over roughly 2,000 square kilometers. Because it burst in the atmosphere, no large crater was formed. Estimates of the energy vary, but it was in the range of several megatons of TNT.
Chelyabinsk, 2013. An object about 20 meters wide entered the atmosphere over Russia and exploded at a height of around 30 km. The shock wave broke windows across a wide area, and about 1,500 people were hurt, mostly by flying glass. Videos recorded by thousands of dashcams made it one of the best-documented meteors in history.
Both events involved objects far smaller than Apophis, and both show that even small asteroids matter. They are also a reminder that the dangerous bodies are not necessarily the giant ones: they are the mid-sized ones that are hardest to find.
Apophis, at about 340 meters, belongs in the 140-meter-and-larger group, but it is not heading for Earth.
Because the comparison shows why planetary defense is a realistic project. We are not trying to stop another Chicxulub, which we already know is not coming. We are watching for smaller objects that we can actually detect and deflect, as NASA showed with the DART mission. Read more in Planetary defense: how humanity learned to move an asteroid and Is Apophis dangerous?
Facts in this article are drawn from public scientific sources. For primary information, see: