Astronomers on Tuesday said that the asteroid designated 2024 YR4 had become the most likely sizable space rock ever forecast to impact planet Earth. The object, first detected in December, is 130 to 300 feet long and expected to make a very close pass of the planet in 2032. Its odds of impacting Earth on Dec. 22 of that year currently stand at 3.1 percent.
That exceeds the threat once posed by Apophis, a much larger asteroid that was discovered in 2004. Astronomers initially calculated its chances of hitting Earth in 2029 at 2.7 percent. Further observations of Apophis reduced the odds of an impact at any time during the next century to zero. But the prospect was, for a time, unsettling.
While 2024 YR4 is far smaller than Apophis, a diminutive asteroid is still capable of causing tremendous devastation. Much depends on where it would enter Earth’s atmosphere.
Although 2024 YR4 would not come close to decimating a country, it could scar or demolish a city with a direct hit. And there is a very slim chance that it might. Much of the object’s estimated track passes over empty ocean, but some possible impact locations are close to large cities like Bogotá, Lagos and Mumbai.
The kinetic energy of an asteroid is a proxy for how destructive its impact would be. And as asteroids mostly move at the same speed — about 38,000 miles per hour — the key variable is its mass.
With just a handful of observations to rely on, astronomers only have a range of estimates for the mass of 2024 YR4. “We don’t know how dense or porous it is, so its mass, and therefore the energy it would release if it strikes Earth’s surface or explodes in the atmosphere, is uncertain,” said Mark Boslough, a physicist at the Los Alamos National Laboratory.
