Thousands of ‘city killer’ asteroids could destroy Earth as boffin admits it ‘keeps me up at night’

Scientists warn that we don’t yet have the means to protect our planet if a deadly space rock heads our way because there is a lack of ‘planetary defence’ funding in space agencies

Humanity is facing a chilling threat as thousands of “city killer” asteroids tear past our planet, Nasa chiefs have warned.

Boffins reckon around 15,000 medium-sized space rocks remain undetected and could be on a collision course with our planet. In 2022, Nasa’s Double Asteroid Redirection Test (Dart) proved we could slam a spacecraft into an asteroid and knock it off course in an emergency.

But the mission’s own boss has warned there is no ready-to-launch system waiting in the wings if a real threat appears. Dart mission chief Dr Nancy Chabot, from Johns Hopkins University in Maryland, US, said: “We worry about these city killer asteroids. Dart was a great demonstration but we don’t have that sitting around ready to go if there was a threat we needed to use it for.

“We don’t know where 50% of the 140-metre asteroids are, which is a concern. We would not have any way to go and actively deflect one right now.

“We could be prepared but I don’t see that investment being made.” She added that space agencies lack the funding to keep planetary defences on standby.

Dr Kelly Fast, Planetary Defense Officer at Nasa HQ, said the mid-sized asteroids are her biggest fear. Speaking at the conference of the American Association for the Advancement of Science (AAAS) in Arizona, she said: “What keeps me up at night is the asteroids we don’t know about. Small stuff is hitting us all the time so we’re not so much worried about that.

“And we’re not so worried about the large ones from the movies because we know where they are. It’s the ones in between, about 140 metres and larger, that could really do regional rather than global damage and we don’t know where they are.

“It’s estimated there are about 25,000 of those and we’re only about 40% of the way through. It takes time to find them, even with the best telescopes.”

This comes as a new mysterious city-sized comet is hurtling towards Earth – just months after “alien” visitor 3i/Atlas whizzed by us. Comet Wierzchoś, also known as C/2024 E1, is rapidly brightening as it approaches its closest point to Earth on Tuesday.

Boffins say the interstellar visitor – first spotted by Polish astronomer Kacper Wierzchoś in March 2024 – has a diameter of around 8.5 miles (13.7 km), around two-thirds the length of Manhattan and around four times the island’s width.

Scientists say it could take several decades or even centuries for it to officially leave the solar system and once it has, it could spend billions of years drifting through the Milky Way, sporadically passing through other alien star systems on its way.

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