Near-Earth asteroids have exceeded quota 40,000: a milestone that shows how much our ability to scan the sky has grown in recent decades. These objects, called Near-Earth Objects (NEOs) can come within 45 million kilometres of Earth's orbit, but only a small proportion pose a real risk.
According to the latest data from the Near-Earth Object Coordination Centre (Neocc) of the European Space Agency, approximately 2.000 of these celestial bodies are classified as “potentially hazardous”. Even in these cases, however, the probability of impact in the next hundred years remains very low – almost always less than 1% – and mainly concerns small objects.
The race to discover it began way back in 1898, when the first asteroid near Earth was identified. Since then, sightings have increased dramatically: as many as 10,000 NEO have been catalogued only in the last three years. “The number of discoveries is increasing exponentially,” explains Luca Conversi, head of ESA's Neocc.
The arrival of new and more powerful telescopes promises to further accelerate this pace. In fact, the scientific community believes it has already identified almost all of the larger asteroids, those over one kilometre in size, which are potentially devastating. The challenge now shifts to bodies of 100–300 metres, which are much more difficult to detect: only 30% would be known.
At the same time, space agencies are stepping up their efforts in planetary defence. ESA is already working on missions such as Hera, heading towards the asteroid Dimorphos to study the impact of NASA's Dart probe, Ramses, which will closely monitor the passage of the asteroid Apophis in 2029, and Neomir, the future “eye in space” capable of observing the region of the sky hidden by sunlight.
Increasingly accurate monitoring and dedicated technologies will make Earth safer: the threat is not imminent, but continuous surveillance is the key to being prepared.
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