CITY-KILLER ASTEROIDS: The Space Rocks Scientists Are Watching Right Now

Every year, massive space rocks barrel past Earth — some large enough to destroy entire cities if they ever strike our planet.

The Silent Threat Above Our Heads

Space is not the empty void many people imagine. Instead, it swarms with rocky debris — chunks of stone and metal that have been drifting through the cosmos since time began. Scientists track thousands of these asteroids as they hurtle past Earth each year. While most are small and harmless, some are massive enough to flatten entire cities if they ever found their target.

These so-called “city-killers” represent one of the most serious threats facing our planet. Unlike earthquakes or hurricanes, asteroid impacts come with little warning and no place to hide. A single space rock, no bigger than a football field, could unleash destruction far beyond anything humans have ever witnessed.

The Distant Future Threat

Asteroid 101955 Bennu holds the distinction of being one of the most thoroughly examined space rocks in existence. NASA’s OSIRIS-REx mission collected samples from its surface and returned them to Earth in 2023, providing scientists with unprecedented data about asteroid composition and behavior.

Bennu measures roughly 490 meters wide — large enough to destroy a metropolitan area. According to updated NASA models, it has a 1-in-2,700 chance of hitting Earth in the year 2182. While that may sound remote, it gives Bennu one of the highest known impact probabilities for a large asteroid.

The space rock orbits the Sun every 1.2 years and makes close approaches to Earth roughly every six years. Scientists are particularly interested in how solar radiation affects Bennu’s path through a phenomenon called the Yarkovsky effect — a tiny but cumulative push caused by heat emissions from its surface.

This unpredictable force makes long-term trajectory modeling extremely difficult, which is why Bennu’s exact path over a century from now remains uncertain. The OSIRIS-REx mission revealed that Bennu’s surface behaves like loose rubble rather than solid rock, which could complicate any future deflection attempts.

Twin Encounters in the Distant Future

Asteroid 1998 OH represents another significant concern for planetary defense experts. This Apollo-class space rock measures between 328 and 656 feet in diameter — large enough to obliterate a city and cause regional devastation if it ever made landfall.

What makes 1998 OH particularly noteworthy are two upcoming close approaches to Earth, expected in 2042 and 2132. During these encounters, the asteroid will pass within 0.03 astronomical units of our planet — roughly 2.8 million miles. While that distance may sound substantial, it places the object firmly in the category of potentially hazardous asteroids.

The asteroid’s elliptical orbit crosses Earth’s path every few years, and while current data shows no immediate impact risk, its trajectory remains sensitive to gravitational influences and solar radiation effects. These subtle forces can alter orbits over time, especially across multiple decades or centuries.

Scientists include 1998 OH in long-term planetary defense simulations, using it to refine impact modeling and response planning. Radar observations during the 2042 flyby could yield more accurate predictions for its 2132 approach.

The Newest Addition to the Watch List

Asteroid 2023 TL4 represents the latest addition to the roster of concerning space rocks. Discovered in late 2023, this asteroid immediately drew attention due to its substantial size — estimated at roughly 1,082 feet wide — and its long-term risk potential.

Within months of discovery, scientists identified a small but notable chance of impact in the year 2119. While the probability remains low at 0.00055%, the asteroid’s destructive potential keeps it on watch lists. A rock of this size would unleash energy many times greater than the most powerful bombs ever created, potentially leveling a city or causing widespread secondary effects.

Like many newly discovered objects, 2023 TL4 carries significant uncertainty. Small changes in its orbital path — caused by gravitational influences or solar radiation — could dramatically alter where it ends up a century from now. The asteroid now forms part of a growing catalog of potentially hazardous objects being tracked with improved detection systems.

The discovery of 2023 TL4 highlights both progress and limitations in planetary defense. Modern sky surveys can spot mid-sized city-busters earlier than ever before, but humanity still has far to go in terms of prevention and mitigation.

The Asteroid That Briefly Ruled the Danger List

Asteroid 2004 VD17 once held the dubious honor of being considered the most dangerous known space rock. With a diameter of around 580 meters, early projections in the 2000s placed a 1-in-1,320 chance of impact in the year 2102.

This probability was high enough to earn the asteroid a Torino Scale rating of 2 — a rare status typically reserved for objects requiring serious tracking and impact assessments. As more data became available, astronomers revised the probability downward and eventually eliminated the 2102 impact scenario entirely.

However, 2004 VD17 has not disappeared from watchlists. Its highly elliptical orbit frequently crosses Earth’s path, and any future gravitational disturbances could still nudge it into a collision course over the coming centuries. The asteroid serves as a classic example of how long-term monitoring remains essential, even for threats that temporarily fall off the radar.

The Massive Wanderer

Discovered in 1990, asteroid 4953 MU stands out due to its impressive size and concerning orbital characteristics. This Apollo-class space rock measures between 984 and 1,968 feet wide, making it significantly larger than the object that caused the 1908 Tunguska event, which flattened 772 square miles of Siberian forest.

The asteroid orbits the Sun every 1.5 years and has several future encounters with Earth scheduled — most notably in 2027 and 2058, when it will pass within a few million kilometers of our planet. While no immediate danger has been forecasted, 1990 MU draws close attention due to its high orbital eccentricity and tendency to frequent Earth’s neighborhood.

Like many large potentially hazardous objects, its orbit could be affected by gravitational interactions with planets or thermal forces that gradually change its trajectory over time. Because of its long observation history, the asteroid serves as an ideal candidate for refining scientific understanding of orbital drift.

Some researchers have suggested 1990 MU could become a target for a future reconnaissance mission, given its size and frequent proximity to Earth. It represents a quiet but massive presence — just a little too close for comfort.

When the Moon Becomes a Target

One of the most unusual threats discovered recently is asteroid 2024 YR4. This space rock, roughly the size of a Boeing 747, caught scientists’ attention not because it might hit Earth — but because it might strike the Moon instead.

When astronomers first spotted 2024 YR4 in late 2024, they calculated a small but troubling chance it could impact Earth in 2032. Fortunately, those odds have dropped to nearly zero. However, the asteroid now carries a 4.3% chance of slamming into the Moon on December 22, 2032.

If this cosmic collision occurs, it would create a crater over a kilometer wide — large enough to see through backyard telescopes. Scientists hope such an impact could provide valuable data about how asteroids behave when they strike solid surfaces. The European Space Agency and NASA are already considering how to study the event if it happens.

The discovery of 2024 YR4 reveals a disturbing truth: many dangerous asteroids remain undetected until they are uncomfortably close to Earth. Even our Moon, which has protected our planet from countless impacts throughout history, is not immune to these cosmic threats.

The Vanishing Threat

Asteroid 2007 FT3 presents one of the most unsettling scenarios in planetary defense: a potentially dangerous space rock that astronomers simply lost track of. Discovered in March 2007, this asteroid was initially assigned a relatively high impact probability for several future dates, including October 3, 2024, and October 2, 2030.

Estimated at approximately 1,082 feet in diameter, its mass and potential speed made it a formidable threat. The asteroid briefly appeared on NASA’s Sentry Risk Table as a potential city-killer. However, the problem with 2007 FT3 is that it was only observed for an incredibly short period — just 1.2 days — before disappearing from view.

This minuscule observation window left massive uncertainty in its predicted orbit. While computer models could suggest dozens of potential close approaches or impacts, the data was too limited to calculate anything with confidence. NASA eventually downgraded the impact probabilities and removed it from high-risk classifications.

2007 FT3 serves as a stark reminder of a frightening reality: many potentially hazardous asteroids are discovered, briefly tracked, and then lost due to short viewing windows or poor observing conditions. Without constant vigilance, we risk repeating this scenario with a space rock we might not have time to stop.

The Return of a Legendary Menace

Few asteroids have captured public attention like 99942 Apophis. Named after the Egyptian god of chaos, this massive space rock once terrorized scientists and the public alike when it was discovered in 2004.

Initial calculations suggested Apophis — measuring between 1,082 and 1,476 feet wide — had a 2.7% chance of striking Earth in 2029. The asteroid briefly received a Level 4 rating on the Torino Scale, a rare classification indicating significant threat of regional destruction. For context, Apophis is large enough to devastate an entire country.

Additional observations eventually ruled out the 2029 collision. Instead, Apophis will swing just 19,644 miles from Earth — closer than some satellites orbit our planet. This near-miss will provide scientists with an unprecedented opportunity to study the asteroid’s structure and behavior.

Despite being cleared for the 2029 approach, Apophis remains under intense surveillance. Some astronomers worry that gravitational interactions with Earth could slightly alter its orbit, potentially setting up dangerous encounters later in the century. The asteroid’s massive size and unpredictable behavior make it a permanent fixture on planetary defense watchlists.

When Multiple Threats Arrive at Once

In May 2025, NASA tracked an unprecedented event: five near-Earth asteroids making close flybys in a single day. While none were large enough to threaten civilization, several measured up to 250 feet wide — roughly the size of major monuments. One object, designated 2025 JO1, passed within just 1.1 million miles of Earth.

While none of these space rocks were on collision courses, the event illustrated how frequently our planet encounters potentially dangerous objects. Among planetary defense experts, such close approaches are viewed as critical training exercises rather than mere curiosities.

Each near-miss provides valuable data for testing tracking software, refining orbital models, and rehearsing emergency alert systems. Had even one of the 2025 flybys been aimed directly at Earth, it could have flattened a major city or triggered devastating tsunamis if it struck the ocean.

Perhaps most unsettling is how routine these events have become. Dozens of city-killer-sized asteroids pass near Earth each year — many discovered only days or weeks in advance. The 2025 cluster reveals how little warning time might be available if a true impact threat were inbound.

The frequency of these encounters underscores the urgent need for improved sky surveys, advanced deflection technologies, and enhanced global coordination. Each near-miss represents not just a scientific opportunity, but a preview of what could one day become a planetary catastrophe.

The Hidden Threats Near Venus

In 2024, astronomers revealed a particularly troubling discovery: Venus may be hiding a group of potentially hazardous asteroids that could pose future threats to Earth. These co-orbital asteroids travel alongside Venus in its path around the Sun, making them extremely difficult to detect due to their proximity to solar glare.

Earth-based telescopes struggle to observe this region of space, meaning some of these threats could be flying completely under the radar. What makes this class of asteroids especially concerning is their potential orbital instability. While they currently follow relatively predictable paths near Venus, any gravitational interaction could send them into Earth-crossing orbits over time.

According to research published in Astronomy & Astrophysics, at least 20 Venus co-orbital asteroids have been identified, including some classified as potentially hazardous to Earth. One of these objects, designated 2020 AV2, currently follows a rare orbit that never crosses Earth’s path — at least for now.

This discovery has intensified calls for space-based detection systems that could observe objects near and inside Earth’s orbit. The Venus co-orbital group represents a significant blind spot in planetary defense — invisible threats that could emerge with little warning.

Source: ListVerse

NOTE: Some of this content may have been created with assistance from AI tools, but it has been reviewed, edited, narrated, produced, and approved by Darren Marlar, creator and host of Weird Darkness — who, despite popular conspiracy theories, is not an AI voice. (AI Policy)