The study combined analytical modeling and long-term simulations, revealing that so-called Venusian co-orbital asteroids can shift between orbital configurations every 12,000 years on average. During these transitions, they may come close enough to Earth to cross its orbit, increasing the risk of impact.
Only 20 such objects have been catalogued to date, most with eccentricities above 0.38, which makes them easier to detect. Researchers believe many more exist with lower eccentricities that keep them hidden near the Sun. Computer models suggest some could approach Earth so closely that eventual impacts become statistically unavoidable over millennia.
"Asteroids about 300 meters in diameter, which could form craters 3 to 4.5 kilometers wide and release energy equivalent to hundreds of megatons, may be hidden in this population," said Valerio Carruba, professor at UNESP and lead author of the study. "An impact in a densely populated area would cause large-scale devastation."
Ground-based telescopes, including the Vera Rubin Observatory in Chile, would see these objects only for brief windows of one to two weeks, separated by months or years of invisibility. Detecting them reliably may require space-based surveys such as NASA's upcoming Neo Surveyor or China's proposed Crown mission, which could scan regions close to the Sun.
The researchers suggest that these bodies originated in the Main Asteroid Belt and were later nudged inward by gravitational interactions, temporarily captured into resonance with Venus. Their orbital instability means they may evolve into Earth-crossing paths or be expelled from the Solar System over time.
Research Report:The invisible threat - Assessing the collisional hazard posed by undiscovered Venus co-orbital asteroids
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