October 2nd, 2025
In the quiet, sunward reaches of our solar system, a celestial detective story is unfolding, one with profound implications for the future of our planet. Astronomers, leveraging data from powerful next-generation ground-based surveys and dedicated space telescopes, have confirmed a long-theorized but elusive population of asteroids: the Venus co-orbitals. These are rocks, some mere meters in diameter, others stretching over a kilometer, that share the orbital path of Venus, dancing in a gravitational waltz with the planet in the resonant space around the Lagrange points leading and trailing its journey around the Sun. For decades, their existence was largely hypothetical, their signals too faint and their positions too close to the Sun’s glare for easy observation. Now, thanks to technological leaps and determined observation campaigns, we have not only confirmed their presence but also begun to understand their dynamics. The most critical finding, and the one that forms the crux of a new paper published today in Planetary Science Journal, is that a significant fraction of these asteroids are not permanently stable. They are, in cosmic terms, temporary companions to Venus, and their gravitational interactions with Earth represent a significant, long-term future impact hazard.
The discovery was spearheaded by a team using the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), which began its ten-year survey of the sky in late 2024. Its ability to rapidly scan the sky and detect faint, moving objects has revolutionized near-Earth object (NEO) astronomy. Combined with targeted observations from the European Space Agency’s Gaia astrometry mission and NASA’s NEO Surveyor space telescope, which specializes in spotting infrared signatures of asteroids close to the Sun, researchers have painted the first clear picture of this hidden population. Dr. Aris Thorne, the lead author of the study from the University of Colorado’s Laboratory for Atmospheric and Space Physics, stated, “For years, the region interior to Earth’s orbit was a blind spot. We knew theoretically that Venus should have a retinue of co-orbital asteroids, much like Jupiter has its Trojans, but actually finding them was like trying to spot a candle flame next to a massive searchlight. The synergy between Rubin’s rapid optical scans and NEO Surveyor’s infrared eyes has finally pulled back the curtain.” The data reveals not just a handful, but likely thousands of these objects, ranging from tiny pebbles to city-sized behemoths, all moving in harmony with Venus’s 225-day orbit.
The mechanics of their orbit are key to understanding both their elusiveness and the threat they may pose. These asteroids are not simply orbiting Venus like a moon; instead, they are trapped in the planet’s Lagrange points—specifically, the L4 and L5 points, which are 60 degrees ahead of and behind Venus in its orbit. At these points, the gravitational pulls of the Sun and Venus create regions of relative stability. However, the inner solar system is a gravitationally chaotic place, with Mercury, Earth, and even Jupiter exerting periodic tugs. This makes the Venusian co-orbital zones far less stable than the Trojan clouds of Jupiter. Dr. Lena Petrova, a dynamicist at the Paris Observatory and a co-author on the paper, explained, “The stability of these objects is measured in thousands or tens of thousands of years, not billions. They exist in a delicate balance. A close pass by Mercury, a resonant kick from Earth—these events can easily perturb them from their safe harbors and send them onto new, and often intersecting, orbital paths.”
This inherent instability is the source of the newly identified long-term hazard. The team’s sophisticated orbital models, run on supercomputers to simulate millions of years of solar system evolution, show a clear and repeated pathway for these objects. When perturbed from their Venus-co-orbital state, a significant percentage—estimated at nearly 20%—are funneled into orbits that cross Earth’s path. The primary conclusion of the research is that the population of Venus co-orbitals represents a major source of future large asteroids that will become Earth-crossers, and thus, potential impactors. This finding reframes our understanding of planetary defense. For decades, the focus has been on the main asteroid belt between Mars and Jupiter as the primary source of NEOs. Now, we must add this “interior reservoir” as a critical, and previously underappreciated, contributor.
It is crucial to emphasize the timeline involved. The hazard identified is not an imminent one. The simulations indicate that the process of an asteroid being nudged out of its Venusian resonance and onto an Earth-crossing path is a slow, gravitational dance that unfolds over centuries and millennia. We are not talking about an object identified today that will hit next year or even next century. Dr. Ben Carter from the Planetary Defense Coordination Office (PDCO) at NASA was quick to provide context: “This research is a monumental step forward in understanding the long-term evolution of the inner solar system, but it should not be a cause for public alarm. The timeframes we are discussing are geological. The probability of a large, civilization-ending asteroid from this population impacting Earth within the next thousand years remains extremely low. What this does is give us a much longer lead time to develop the technologies and strategies needed to deal with them.” In essence, the study shifts the focus of planetary defense from reactive to profoundly proactive, looking thousands of years into the future.
The “nearly invisible” nature of these asteroids adds a layer of complexity to the challenge. Because they orbit primarily inside Earth’s orbit, they spend most of their time in the daytime sky as seen from our planet, lost in the Sun’s overwhelming glare. Their visible-light observations are limited to brief windows during twilight, just after sunset or before sunrise, when they are low on the horizon and their light must pass through the thickest part of our atmosphere. This is where the infrared capabilities of instruments like NEO Surveyor become invaluable. Dr. Thorne elaborated, “These asteroids are heated by the nearby Sun, and they glow brightly in the infrared, which passes through our atmosphere more readily than visible light during those critical twilight observation periods. This is our key to tracking them. We are now in a position to begin a systematic census, cataloging the largest and most potentially hazardous members of this population.”
The bold and unequivocal call to action from the scientific community is for a sustained and enhanced survey program focused on the inner solar system. The success of the current observatories has proven the concept, but a more dedicated effort is needed to achieve a comprehensive catalog. Proposals are already being drafted for a follow-up space mission, tentatively named the “Inner Planet Asteroid Surveyor” or IPAS, which would be positioned in an orbit similar to Venus’s to conduct a detailed, close-range census. The goal is to find and track 90% of the Venus co-orbitals larger than 140 meters, the size at which an impact would cause regional devastation. This would mirror the success of similar surveys for NEOs that orbit outside Earth’s path.
Furthermore, this discovery has invigorated the field of asteroid deflection research. With lead times measured in millennia, humanity would have a vast array of options for dealing with a future identified threat. Dr. Kenji Tanaka, lead engineer for the upcoming NASA DART-2 mission concept, noted, “A thousand years of warning changes everything. We wouldn’t need to use a kinetic impactor or a nuclear device for a brute-force shove. We could employ a ‘gravity tractor’—a spacecraft that simply hovers near the asteroid for years, using its tiny gravitational pull to gradually nudge the object onto a safer path. It’s a gentle, precise, and entirely feasible method when time is on your side.”
