Two decades after NASA was tasked with tracking near-Earth asteroids, scientists are now warning of a new threat: asteroids co-orbiting with Venus. These asteroids—circling the Sun along a similar path—are capable of colliding with Earth, according to a recent study co-authored by multiple scientists.

Venus co-orbital asteroids are classified as potentially hazardous if they are at least 140 meters wide and pass within 0.05 astronomical units of Earth’s orbit. Though they follow Venus’s path, these elusive bodies can drift toward Earth and evade current detection systems.

NASA scientists surveyed a region extending 1.3 astronomical units (approximately 194 million kilometres).

Titled “The Invisible Threat: Assessing the Collisional Hazard Posed by the Undiscovered Venus Co-Orbital Asteroids,” the study reveals that low-eccentricity asteroids are particularly difficult to detect from Earth.

Venus’s co-orbitals often have eccentric orbits—a pattern believed to result more from observational challenges than from their true orbital characteristics.

To investigate further, researchers created simulated “clones” of these asteroids and ran orbital models spanning 36,000 virtual years.  They found that asteroids with low eccentricities and low inclinations could indeed cross Earth’s orbit and pose a collisional hazard.

"Twenty co-orbital asteroids of Venus are currently known," the authors write. "Co-orbital status protects these asteroids from close approaches to Venus, but it does not protect them from encountering Earth." 

How real is the risk?

Detecting these objects from Earth is difficult due to the Sun’s glare, which obscures them for most of their orbit. Observations become easier when these asteroids approach Earth and move into more visible regions of the sky.

Several missions have been proposed, including to the sun-Earth or sun-Venus orbit. The upcoming Vera Rubin Observatory in Chile, set to begin operations in July 2025, may detect some of these objects during favourable conditions, but the study suggests this won’t be sufficient for comprehensive tracking.

"While surveys like those from the Rubin Observatory may be able to detect some of these asteroids in the near future, we believe that only a dedicated observational campaign from a space-based mission near Venus could potentially map and discover all the still 'invisible' PHA among Venus' co-orbital asteroids," the researchers reveal.

The researchers further argue that a dedicated space-based mission, particularly one positioned in Venus’s orbit and facing away from the Sun, would be the most effective solution. Such a mission could overcome visibility issues and allow for consistent tracking of these elusive objects.

With some Venus co-orbitals potentially capable of city-destroying impacts, the study highlights the urgency of improving detection methods to identify and monitor these “invisible” threats.

Even a single asteroid measuring 150 meters across could release energy equivalent to hundreds of megatons of TNT. This, upon impact, is thousands of times more powerful than the atomic bombs dropped during World War II.