Could an asteroid hit Earth?

Space is not empty. Dust and small stones hit our atmosphere every day, and we see them as shooting stars. Larger rocks are rarer, and the larger they are, the rarer they get.

A rock about 10 metres across arrives about once every 10 years. It makes a brilliant fireball and a bang, and can break windows. One about 50 metres across comes every between 1,000 and 1,500 years and could flatten a city.

The truly dangerous ones are rarer still. A 1-kilometre asteroid hits about once every between 520,000 and 700,000 years. One 10 kilometres across, like the one that ended the dinosaurs, comes every between 100 million and 120 million years. These are averages, not a timetable: Earth is never "due" for one.

When a new asteroid is found, its orbit is fuzzy at first. NASA's Sentry system and ESA's own risk list run that fuzzy orbit forward a hundred years. If any possible path touches Earth, the asteroid goes on the list with a small chance of impact.

As of 4 November 2026, Sentry lists 2,230 asteroids. The highest rating among them on the Torino scale, which runs from 0 (no hazard) to 10, is 0.

More sightings shrink the fuzz. Usually Earth then falls outside it, and the chance drops to zero. That happened with 2024 YR4. In early 2025 it briefly had a small chance of hitting us in 2032. More sightings ruled out an impact in 2032, and Sentry removed it in March 2026. Its pass on 22 December 2032 now misses both Earth and the Moon in NASA's data.

Apophis is a large asteroid. Soon after it was found, it briefly looked like it might hit us. Better measurements removed it from the risk list in 2021: NASA says it poses no risk for at least 100 years.

On 13 April 2029, it will pass about 38,000 kilometres from Earth's centre. That is closer than the satellites in geostationary orbit, about 36,000 kilometres up. It is about 10 times closer than the Moon.

On 26 September 2022, NASA's DART spacecraft flew into Dimorphos, a small moon of the asteroid Didymos. Neither threatened Earth. The test was whether a spacecraft could push one.

It could. DART shortened Dimorphos's orbit by 32m 00s. That is a small change, but given years of warning, a small push is enough to make an asteroid miss.

Surveys have found more than 90% of the near-Earth asteroids larger than 1 kilometre, the ones that could cause global harm. None of them is on a path to hit us.

Smaller ones, around 140 metres, are harder to see, and many are still unfound. That is the work of the Rubin Observatory and NASA's planned NEO Surveyor telescope. We are the first living things on Earth that can see a rock coming, years ahead, and do something about it.