The Most Dangerous Asteroids in History: What We’ve Faced, What We’ve Feared, and What We’ve Learned

When people ask about “the most dangerous asteroids,” they usually mean one of two things: the objects that actually hit us and did outsized damage, or the near-Earth asteroids that—based on the best data available at the time—looked frightening until more observations dialed the risk down. Both kinds matter. The former are hard, sobering case studies; the latter are the stress tests that sharpen our detection networks, models, and playbooks for planetary defense.

This long-form guide traces both threads. We’ll look at the worst known asteroid impact in Earth’s geologic record; two historic modern-era blasts that arrived with little warning; and a handful of infamous “risk list” asteroids—Apophis, 1950 DA, Bennu, 2009 FD, 2011 AG5, and 2013 TV135—whose stories show how scientific uncertainty narrows over time. Along the way, we’ll demystify the threat scales (Torino and Palermo), highlight what constitutes “danger” in practical terms, and end with what’s being done now to keep an eye on the sky.

How We Measure Asteroid Danger

Before we weigh historical threats, it helps to understand how risk is communicated. Two scales come up again and again.

The Torino Scale is a 0-to-10 color-coded index intended for public communication about potential impact events within the next 100 years. A “0” means no risk or a rock that would burn up on entry; a “10” means a certain, global-scale catastrophe. Most objects that briefly cause a stir spend their lives at 0 and sometimes touch 1, which means “normally no cause for public concern,” pending more observations. cneos.jpl.nasa.gov+1

The Palermo Technical Impact Hazard Scale is the nerdier sibling: a logarithmic measure that compares a potential impact’s risk to the background risk of impacts of the same time window. A Palermo score of 0 means the risk is equal to that background; negative numbers are lower than background (typical for most “worry cases”), and positive numbers—rare—would be higher than background. Palermo is a tool for professionals, not headlines. cneos.jpl.nasa.govVikipedija

Taken together, these scales explain why “most dangerous” is tricky: an asteroid might look ominous early on (a higher Torino category or less-negative Palermo score) and then settle into benign territory after follow-up tracking improves its orbit.

The Catastrophic Yardstick: Chicxulub and the Day the World Changed

The benchmark for global asteroid danger is the Chicxulub impact, which struck what is now Mexico’s Yucatán Peninsula about 66 million years ago. Geophysics and drilling show a buried, multi-ring crater roughly 180 kilometers across, consistent with an impactor about 10 kilometers in diameter. The energy release, atmospheric effects, and the aftermath—dust veils, wildfires, acid rain, and a “long winter”—are widely linked to the mass extinction that ended the age of non-avian dinosaurs. Iridium-rich layers and shocked minerals provide a global fingerprint of the event. Chicxulub remains the textbook example of a “planet killer.” pubs.usgs.govUSGSscience.org

Chicxulub is useful not because we expect a repeat anytime soon, but because it anchors the high end of the risk spectrum. Planet-scale impactors are extraordinarily rare on human timescales—but they show what we mean by existential risk versus regional or local disasters. NSF – National Science Foundation

Modern Wake-Up Calls: Tunguska and Chelyabinsk

Tunguska (1908): A Forest Flattened

On June 30, 1908, over the Tunguska region of Siberia, a small asteroid or comet exploded in an airburst that flattened roughly 2,000 square kilometers of forest. Energy estimates have varied over the decades; modern assessments cluster around the range of tens to more than a hundred kilotons of TNT—orders of magnitude below Chicxulub but devastating on a regional scale. Because the object detonated at altitude, no large crater remains, and the event is reconstructed from tree-fall patterns, eyewitness accounts, and geophysical studies. Tunguska is the canonical reminder that tens-of-meters objects can do real damage—and that “no crater” doesn’t mean “no impact.” VikipedijaNASA

Chelyabinsk (2013): A City-Size Shockwave

On February 15, 2013, a stony ~18-meter asteroid exploded over Chelyabinsk, Russia. The airburst released hundreds of kilotons of energy, generating a shockwave that shattered windows and injured over a thousand people—mostly from flying glass. Chelyabinsk was a near-miss in the best sense: no fatalities, but an expensive, unexpected reminder that small asteroids approach from the daylit sky and can evade ground-based telescopes. Sixteen hours later, a different asteroid, 2012 DA14 (now named 367943 Duende), safely skimmed past Earth at roughly 27,700 km above the surface—closer than geosynchronous satellites. The coincidence was just that—a coincidence—but together the events catalyzed political momentum for planetary defense. NASA Jet Propulsion LaboratoryVikipedija+1cneos.jpl.nasa.gov

The Famous Near-Misses (and Why They Matter)

The following asteroids are “dangerous” in the historically meaningful sense: at one point each presented relatively high (or highly publicized) risk indicators before being retired to low-risk status. Their stories reveal how risk evolves as we collect more data.

99942 Apophis: The Rock That Scared a Generation—Then Relented

Discovered in 2004, Apophis quickly became the poster child for asteroid anxiety after preliminary analyses gave it unnervingly high odds—for a while—of hitting Earth in 2029. As radar and optical observations tightened the orbit, the 2029 threat vanished, but attention shifted to whether that close pass might tweak Apophis into a later collision course. In March 2021, after new radar data and analyses, NASA removed Apophis from the Sentry risk list: no impact for at least 100 years. Apophis will still pass astonishingly close—about 31,600 km above Earth—on April 13, 2029, bright enough to see with the naked eye across parts of the Eastern Hemisphere. Scientifically? It’s a once-in-a-lifetime laboratory flyby. Practically? It’s safe. NASAVikipedija

Why Apophis was “dangerous”: It briefly rose to a non-zero Torino category and dominated public attention. It also forced major upgrades in how we coordinate rapid follow-up observations and evaluate keyhole passages—small regions of space where a close approach could set up a later impact.

(29075) 1950 DA: The Long Game

Rediscovered in 2000 after being lost since 1950, 1950 DA drew attention for a potential impact in 2880—almost nine centuries out. For years, it had one of the highest Palermo scores, not because an impact was likely on an absolute scale, but because the event would be so energetic and the time horizon so long that uncertainty loomed large. As with many long-arc cases, better modeling (including subtle forces like thermal “Yarkovsky” drift) has steadily refined the odds downward, most recently in 2022. The current assessments push the risk comfortably below levels of concern for the foreseeable future. cneos.jpl.nasa.gov

Why 1950 DA was “dangerous”: Not imminent danger, but a case that stretched our computational tools and underscored how tiny non-gravitational forces matter over centuries.

(101955) Bennu: The OSIRIS-REx Target With a Tiny but Real Probability

NASA’s OSIRIS-REx mission visited Bennu, sampled it, and transformed it from a blurry point of light into a richly characterized world. That science fed straight into hazard assessment: in 2021, JPL reported a 0.057% cumulative impact probability for Bennu through 2300, with a particular date—September 24, 2182—carrying an estimated 0.037% (about 1-in-2,700) chance. That’s still small, but unusually well-constrained thanks to spacecraft tracking, gravity field mapping, and detailed modeling of sunlight’s tiny push. The 2135 Earth flyby will decide which of many possible “gravitational billiards” Bennu will take next; most paths mean a miss, a very few would point toward Earth later. NASA Jet Propulsion LaboratoryNASA Scientific Visualization Studio

Why Bennu is “dangerous”: It’s the rare case where a precise (if still very small) probability exists for a specific late-22nd-century date—plus we have ground truth on its structure and surface, vital for any future deflection planning.

(410777) 2009 FD: A Sentry Table Regular, Now Retired From Worry

For years, 2009 FD lingered near the top of risk tables because of possible late-22nd-century keyholes. Its maximum Palermo rating was modest (negative, but relatively less negative than most). As observational arcs lengthened and dynamical models improved, the projected impact scenarios evaporated; by 2019, the once-discussed 2185 concern had been essentially ruled out. 2009 FD is a classic of the “it looked spooky until we actually had data” genre. Vikipedija

Why 2009 FD was “dangerous”: It taught patience. Early rankings are not destiny; they’re invitations to observe harder.

2011 AG5: A Brief Flurry, Then a Safe Flyby

Discovered in 2011, 2011 AG5 made headlines in 2012 when early calculations suggested a small (but non-zero) chance of a 2040 impact. NASA’s NEO office convened a workshop; better observations soon erased the concern, and the object indeed flew past safely in 2023 at millions of kilometers’ distance. If you remember breathless “1-in-500” headlines from the time, you’re remembering the early uncertainty window—not the final word. NASA Jet Propulsion LaboratoryGizmodo

Why 2011 AG5 was “dangerous”: It illustrated why rapid follow-up (especially radar) is priceless, and why agencies emphasize that Torino “1” isn’t cause for panic.

2013 TV135: From Torino 1 to Background Noise—In Weeks

Discovered in October 2013 after a September flyby, 2013 TV135 briefly earned a Torino Scale 1 rating while its orbit was still fuzzy. Within weeks, additional data drove it back to 0. The object passed ~6.7 million km from Earth in September, and that was that. A reality check from JPL at the time emphasized that early “Torino 1” objects are common and almost always fade to zero with follow-up. NASA Jet Propulsion LaboratoryVikipedija

Why 2013 TV135 was “dangerous”: It wasn’t, in hindsight—but it’s a clean example of how the system is supposed to work.

The Close-Shave That Wasn’t: 2012 DA14 (367943 Duende)

Because it zipped closer than many satellites, 2012 DA14 deserves its own short entry. At about 45–50 meters across, it was large enough to be destructive if it had entered the atmosphere over a populated area—but it didn’t. The February 15, 2013 close approach, at roughly 27,700 km above Earth, was precisely predicted and carefully tracked; no impact was ever expected. The timing—just hours after the Chelyabinsk airburst—was surreal but coincidental. cneos.jpl.nasa.govNASA Jet Propulsion Laboratoryui.adsabs.harvard.edu

What These Cases Teach Us About “Danger”

1. Small asteroids are frequent; big ones are rare. Tunguska- and Chelyabinsk-class objects (tens of meters) are the main near-term concern. They don’t end civilizations, but they can devastate a city or region. Chicxulub-class impactors (multi-kilometer) are globally catastrophic but exceptionally uncommon on human timescales. Planetary defense is a probability game: lots of small tickets, vanishingly few big ones. (Chicxulub remains the poster child for the extreme tail of the distribution.) pubs.usgs.govNASA Jet Propulsion Laboratory
2. Early risk is not final risk. Apophis, 1950 DA, 2009 FD, 2011 AG5, and 2013 TV135 all looked worse before they looked boring. This is how orbital mechanics works: fresh discoveries often have short “arcs” (few days of data), which yields a fan of possible futures. As radar and additional nights of optical tracking come in, that fan narrows, and the scary branches usually vanish. That’s why both the Torino and Palermo scales are paired with strong caveats in official explanations. cneos.jpl.nasa.gov+1
3. Close isn’t the same as dangerous. Duende’s record-setting skim was dramatic and completely non-hazardous—a triumph of prediction, not a “near-death” experience. The key question is not distance alone but whether the orbit crosses Earth’s at the same time. cneos.jpl.nasa.gov
4. Physics beyond gravity matters over long times. For century-scale predictions, subtle forces like the Yarkovsky effect—sunlight warming the asteroid and re-radiating heat—can noticeably shift orbits. Bennu and 1950 DA are case studies in why spacecraft reconnaissance, radar, and thermophysical modeling matter. NASA Jet Propulsion Laboratory

How We Find and Track the Threat

A global network of surveys—current and coming online—feeds the risk pipeline. Wide-field telescopes scan the sky nightly; objects get provisional designations; follow-up teams refine the orbits; and centralized systems like NASA’s Sentry and ESA’s Risk List crunch probabilities and publish updates.

• Sentry continuously computes impact probabilities for newly discovered near-Earth objects and updates the Torino and Palermo metrics when relevant. If you’ve seen headlines about asteroids being “removed from the risk list,” that list is Sentry’s. cneos.jpl.nasa.gov
• ESA’s Risk List mirrors the same mission, maintaining a live catalog of any object with a non-zero impact probability. NEO

The “find–track–assess” loop is the heart of modern planetary defense. Every time a high-profile object like Apophis is downgraded, it’s not a false alarm—it’s the system working.

What If One Really Were on a Collision Course?

The good news: we’re not helpless. NASA’s DART mission demonstrated in 2022 that a kinetic impactor can change an asteroid’s motion by hitting it at high speed. That proof-of-concept, combined with reconnaissance missions (OSIRIS-REx at Bennu and the forthcoming OSIRIS-APEX at Apophis), builds the path from detection to deflection. In a scenario involving a small, years-out threat, a DART-like nudge could turn a bull’s-eye into a miss. For larger objects or tighter timelines, more complex options (gravity tractors, multiple impactors) would be considered. (While DART isn’t cited above, the logic connects directly to the Bennu and Apophis cases, where detailed physical knowledge enables practical planning.)

Profiles in “Danger”: A Concise Roll-Call

Chicxulub Impactor (≈10 km) — Set the extinction event that ended the Cretaceous; crater diameter ≈ 180 km. The standard for “planet-killer.” pubs.usgs.govUSGS

Tunguska Object (tens of meters) — Airburst over Siberia, 1908; flattened ~2,000 km²; energy on the order of ~150 kt by some modern estimates. NASA

Chelyabinsk Meteoroid (~18 m) — Airburst over Russia, 2013; hundreds of kilotons released; thousands injured by shattered glass. NASA Jet Propulsion Laboratory

2012 DA14 / 367943 Duende (~45–50 m) — Record-setting 27,700 km flyby on the same day as Chelyabinsk; close but harmless. cneos.jpl.nasa.gov

99942 Apophis (~450 × 170 m) — Once a 2029 scare; now confirmed safe for 100+ years; will pass ~31,600 km above Earth on April 13, 2029. NASAVikipedija

(29075) 1950 DA (~1–2 km) — Historic long-term concern for year 2880; risk refined downward with improved modeling (2022 update). cneos.jpl.nasa.gov

(101955) Bennu (~490 m) — OSIRIS-REx target; cumulative 0.057% impact chance by 2300; 0.037% on Sept 24, 2182; highly studied and modeled. NASA Jet Propulsion Laboratory

(410777) 2009 FD (~400 m) — Once near the top of risk tables; potential 2185 impact scenarios ruled out with later data. Vikipedija

2011 AG5 (~140 m) — Early 2040 concern erased with follow-up; safe flyby in 2023. NASA Jet Propulsion Laboratory

2013 TV135 (~450 m) — Temporary Torino 1 rating; downgraded after weeks; no known risk. NASA Jet Propulsion Laboratory

Why So Many Scares Turn Out Fine

To the uninitiated, it can seem like “we keep crying wolf.” In reality, well-publicized downgrades are a sign that:

• We’re finding more objects than ever. Increased discovery means more early-stage uncertainties. Most will fade to zero risk—exactly as predicted by the math. cneos.jpl.nasa.gov
• Follow-up is working. Radar ranging can shrink orbital uncertainties by orders of magnitude in a single night; optical follow-up extends arcs; spacecraft flybys and rendezvous give physical properties that improve trajectory modeling (e.g., Yarkovsky on Bennu). NASA Jet Propulsion Laboratory
• Scales are conservative by design. A temporary Torino 1 is a placeholder, not a prophecy. Palermo’s negative numbers often look ominous to lay readers, but they simply say “less risky than the background.” cneos.jpl.nasa.govVikipedija

Lessons for Risk Communication

1. Use dates and distances. Saying “close” is meaningless without numbers. Apophis at ~31,600 km in 2029 is spectacular and safe; Duende at 27,700 km was a similar story. NASAcneos.jpl.nasa.gov
2. Explain uncertainty. Early arcs yield wide cones of possibility; later arcs shrink them. Headlines often land during the “wide cone” phase. That’s not hype; that’s the process.
3. Separate impact energy from impact probability. A big rock with a vanishingly small chance over centuries (e.g., 1950 DA) should not be conflated with a small rock with a non-zero chance in a few decades (a hypothetical Bennu-like case). Both matter, but in different ways. cneos.jpl.nasa.govNASA Jet Propulsion Laboratory

The State of Planetary Defense (and Why It’s Getting Better)

• Survey Power: New and upgraded surveys (including forthcoming wide-field facilities) will push completeness for 140-meter-class NEOs higher, the size range that threatens cities and regions.
• Impact Monitoring: Systems like Sentry and ESA’s Risk List automate long-term risk computation, catching low-probability but high-consequence scenarios early. cneos.jpl.nasa.govNEO
• Physical Characterization: Missions like OSIRIS-REx improve our “know your rock” quotient—critical for designing any deflection campaign. Bennu’s precisely measured orbit and Yarkovsky drift are the gold standard here. NASA Jet Propulsion Laboratory
• Deflection Demos: The DART kinetic impact in 2022 showed we can change a small asteroid’s motion. Combine that with early detection and you have a credible plan for many realistic threats.

So… Which Were the Most Dangerous?

If we define “dangerous” by realized damage, then Chicxulub is the all-time champion by a country mile, with Tunguska and Chelyabinsk as modern-era reminders that sub-100-meter objects can pack a punch. If we define it by credible risk at the time of assessment, then Apophis, 1950 DA, Bennu, 2009 FD, 2011 AG5, and 2013 TV135 top the list of historically important near-misses—objects that forced us to refine models, mobilize follow-up, and improve communication.

Crucially, those “dangerous” near-misses did their job: they made planetary defense better.

Final Takeaways

1. The sky is not falling—but it is active. Earth lives in a cosmic shooting gallery. Most bullets miss; a few ricochet through the atmosphere; a vanishingly small number hit the target. The job of modern astronomy is to spot as many bullets as possible early.
2. Danger is dynamic, not dramatic. Risk changes with every observation. The headlines that announce downgrades aren’t backpedaling; they’re science tightening the screws.
3. Prepared beats scared. From Sentry’s automated risk assessments to missions like OSIRIS-REx and DART, we’re building a chain from discovery to deflection. The more Apophis-like stories we have—big headlines, careful follow-up, safe outcomes—the better positioned we are the day a “Torino 2 or 3” actually sticks.

If you want to keep tabs on the truly worrisome stuff, watch the official sources that update in real time and explain their methods plainly—the NASA/JPL CNEOS Sentry pages and ESA’s Risk List. They won’t make for breathless clickbait, but they’ll tell you exactly what you need to know, when you need to know it. cneos.jpl.nasa.govNEO

Sources & Further Reading

• NASA/JPL CNEOS: Apophis ruled out for a century; 2029 pass at ~31,600 km; public risk update (Mar 2021). NASA
• Wikipedia summary corroborating Apophis flyby distance (contextual background). Vikipedija
• JPL News: Bennu impact probability refined with OSIRIS-REx data (Aug 2021); NASA SVS visualization of 2182 scenario (1-in-2,700). NASA Jet Propulsion LaboratoryNASA Scientific Visualization Studio
• JPL/CNEOS: 2012 DA14 close approach (Feb 2013). cneos.jpl.nasa.gov
• Wikipedia summary (Duende) confirming distance and timing; useful for general readers. Vikipedija
• JPL News: Chelyabinsk event details (Feb 2013). NASA Jet Propulsion Laboratory
• NASA History: Tunguska overview and modern energy estimate. NASA
• USGS and peer-reviewed summaries: Chicxulub crater size and evidence. pubs.usgs.govUSGS
• JPL: 2013 TV135 reality check; downgraded from Torino 1 to 0. NASA Jet Propulsion Laboratory
• CNEOS: Torino and Palermo scale explanations; Sentry impact monitoring. cneos.jpl.nasa.gov+2cneos.jpl.nasa.gov+2
• Background on 2009 FD downgrading and 2185 scenario. Vikipedija
• JPL/CNEOS: 1950 DA long-term update; further risk reduction (Mar 2022). cneos.jpl.nasa.gov

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