Asteroid Impact

Overview

Every day, Earth is pelted by roughly 100 tons of space debris — mostly dust and sand-grain-sized particles that burn up harmlessly in the atmosphere. But the solar system also contains millions of larger objects whose orbits cross Earth’s path. The question isn’t if a significant asteroid will strike again — it’s when, and how big.

Impact Categories by Size

For reference, the largest nuclear weapon ever detonated — the Tsar Bomba — yielded 50 megatons. A 1 km asteroid impact releases energy equivalent to roughly 2,000 Tsar Bombas simultaneously.

The Torino Scale

The Torino Scale rates asteroid threats from 0 (no hazard) to 10 (certain collision with global catastrophe). As of 2025, no known object rates above 0 on the Torino Scale for the next century. But “known” is the operative word — NASA estimates it has catalogued roughly 40% of near-Earth asteroids larger than 140 meters.

Historical Impacts

Chicxulub (66 million years ago): A 10–15 km asteroid struck what is now Mexico’s Yucatán Peninsula at roughly 20 km/s (45,000 mph). The impact released energy equivalent to 10 billion Hiroshima bombs, triggered magnitude 11+ earthquakes, spawned mega-tsunamis over 100 meters tall, and ejected billions of tons of dust and sulfur into the atmosphere. The resulting impact winter lasted years, collapsing photosynthesis-dependent food chains. Roughly 76% of all species went extinct, including all non-avian dinosaurs.

Tunguska (1908): A 50–60 meter object exploded at approximately 5–10 km altitude over Siberia, flattening 2,150 km² of forest — an area the size of a major city. The airburst released 10–15 megatons of energy, roughly 1,000 times the Hiroshima bomb. Had it arrived four hours later, Earth’s rotation would have placed St. Petersburg in the blast zone, killing hundreds of thousands.

Chelyabinsk (2013): A 20-meter asteroid entered the atmosphere at 19 km/s and exploded at ~30 km altitude over Chelyabinsk, Russia. The airburst released approximately 500 kilotons of energy — 30 times Hiroshima. The shockwave shattered windows across six cities, injuring over 1,600 people (mostly from flying glass). No one saw it coming — the object approached from the direction of the Sun, invisible to ground-based telescopes.

Early Warning: Planetary Defense Infrastructure

Who’s Watching the Sky?

Several organizations form humanity’s asteroid detection network:

• NASA’s Planetary Defense Coordination Office (PDCO): Established in 2016, coordinates all NASA-funded Near-Earth Object (NEO) detection efforts. Manages the Sentry impact monitoring system.
• NASA’s NEO Surveyor Mission: An infrared space telescope (launched 2028) designed to find 90% of NEOs larger than 140 meters within a decade.
• ESA’s Planetary Defence Office: Operates the European Space Agency’s NEO coordination centre and the Flyeye telescope network.
• Catalina Sky Survey & ATLAS: Ground-based survey telescopes that scan the sky nightly. ATLAS can provide 1–3 weeks warning for a Chelyabinsk-sized object, and months to years for larger ones.
• B612 Foundation: A private nonprofit advocating for asteroid detection and deflection technology.

Detection Timeline — What Warning Can You Expect?

• Small airbursts (10–30 m): Hours to zero warning. Chelyabinsk had none. These are the most likely impact events in your lifetime.
• City-killers (50–140 m): Days to months if discovered on approach; potentially years if discovered during a previous orbit.
• Large impactors (140 m+): Years to decades of warning for catalogued objects. This is where deflection missions become possible.

The critical takeaway: For the most likely impact event — a small to medium airburst — you will probably have no advance warning. Your survival depends on general preparedness, not event-specific planning.

Immediate Effects: The First Hours

The effects of an asteroid impact scale dramatically with size. Here’s what happens in the immediate aftermath of a significant (1 km+) land impact:

The Impact Itself (T+0 to T+10 seconds)

The asteroid strikes the surface at 15–25 km/s, instantly vaporizing itself and a roughly equal mass of target rock. A transient cavity forms, tens of kilometers across and deep. The energy release is so extreme that rock behaves like a fluid. A blinding flash — brighter than the sun at hundreds of kilometers — ignites fires by thermal radiation alone.

Survival radius for a 1 km impactor:

• 0–50 km: Total annihilation. Nothing survives.
• 50–300 km: Extreme overpressure (>10 psi). Most structures collapse. Fatal burns from thermal radiation.
• 300–1,000 km: Moderate to severe damage. Windows shattered, weak structures collapse, scattered fires. Survivable in reinforced shelter.
• 1,000+ km: Light damage from air blast, significant seismic shaking.

Seismic Shockwave (T+30 seconds to T+5 minutes)

A 1 km asteroid impact generates an earthquake of approximately magnitude 7–8, felt worldwide. Within 1,000 km, violent ground shaking lasts for minutes — causing building collapses, landslides, and infrastructure failure.

Ejecta and Re-Entry (T+5 minutes to T+2 hours)

Billions of tons of pulverized rock are launched on ballistic trajectories. Larger fragments fall nearby; finer ejecta reaches the upper atmosphere and re-enters globally. For an extinction-class event, re-entering ejecta heats the upper atmosphere enough to ignite widespread fires — the so-called “broiler effect.” Surface temperatures can briefly spike by hundreds of degrees.

Tsunami (Ocean Impact)

If the asteroid strikes ocean (71% probability for random impact):

• A 1 km asteroid generates tsunamis 100–300 meters high near the impact site
• Waves of 10–30 meters at 1,000 km distance
• Coastal regions worldwide face dangerous wave activity for 12–24 hours
• Inland areas above 30 meters elevation are generally safe from direct wave action

Firestorm (T+1 hour to T+48 hours)

Thermal radiation, re-entering ejecta, and secondary ignition sources combine to start massive fires. For a civilization-level event (1 km+), fires may consume millions of square kilometers of forest and grassland, injecting enormous quantities of soot into the stratosphere — compounding the coming impact winter.

Impact Winter: The Long Dark

This is where an asteroid impact transitions from a regional catastrophe to a global existential threat. An impact winter shares many characteristics with nuclear winter, and the survival strategies overlap significantly.

The Mechanism

A large impact (1 km+) injects billions of tons of dust, soot, and sulfur aerosols into the stratosphere. Unlike tropospheric particles (which rain out in days), stratospheric particles remain suspended for months to years. This creates a global dust veil that:

• Blocks sunlight: A 1 km impactor could reduce surface sunlight by 20–40% for 6–18 months. A 10 km impactor (Chicxulub-class) blocks over 90% of sunlight for 1–2 years.
• Drops temperatures: Global average temperatures fall 5–15°C for a 1 km event; 10–30°C for a Chicxulub-class event. Even summer temperatures may remain below freezing in temperate zones.
• Destroys the ozone layer: Nitrogen oxides generated by the impact and fires catalytically destroy stratospheric ozone, allowing dangerous UV radiation levels once the dust clears.
• Triggers acid rain: Sulfur and nitrogen compounds create sulfuric and nitric acid rainfall, damaging remaining vegetation and contaminating water sources.

Agricultural Collapse

This is the primary kill mechanism for humanity in a large impact scenario:

• Growing seasons eliminated: Sub-freezing temperatures and minimal sunlight halt photosynthesis. Most crops fail completely.
• Timeline: Even a “moderate” impact winter (1–2 km asteroid) could eliminate one to two full growing seasons globally. A Chicxulub-class event could suppress agriculture for 3–10 years.
• Cascading failure: Global food reserves typically last 3–6 months. After that, famine becomes the dominant cause of death — potentially killing billions within the first year.

Shelter & Survival: The First 72 Hours

If You See the Flash

If you witness an extremely bright flash on the horizon (brighter than the sun, lasting several seconds), you are within range of an impact’s effects:

1. Do NOT look at the flash. It can cause permanent retinal burns at hundreds of kilometers.
2. Drop and cover immediately. The blast wave travels at roughly 1 km every 3 seconds. You may have seconds to minutes depending on distance.
3. Get below ground if possible. Basements, subways, underground parking structures.
4. Stay away from windows. Flying glass caused nearly all injuries at Chelyabinsk.
5. Protect your airway. Dust, debris, and potentially toxic particulates will fill the air.

No-Warning Airburst (Chelyabinsk-Type)

Since the most likely impact scenario comes with zero warning:

• If you suddenly see an intensely bright light through a window, move away from the window immediately. You have approximately 1–3 minutes before the shockwave arrives.
• Drop below window level or move to an interior room.
• Cover your face and head.
• After the shockwave passes, assess for injuries — primarily cuts from glass.

First 72 Hours After a Major Impact

For a large, confirmed impact (assuming you’re outside the immediate kill zone):

Hour 1–6:

• Shelter in place underground or in reinforced structures
• Account for family/group members
• Assess structural damage before moving through buildings
• Begin monitoring any available communications (emergency radio, satellite phone)
• Treat injuries — expect lacerations, crush injuries, burns, and blast-related trauma

Hour 6–24:

• Secure water supply. Fill every available container. Municipal water may fail quickly.
• Secure food stores. Begin rationing immediately if the impact is large.
• Seal shelter from dust infiltration — duct tape, plastic sheeting over windows and vents
• If ejecta is re-entering (visible as streaks of fire across the sky), remain sheltered
• Avoid open flames near damaged structures (gas leaks)

Hour 24–72:

• Assess the scope of the event via radio/communications
• Begin organizing with neighbors and local community
• Identify medical resources and personnel
• Secure and inventory all food and water
• Begin planning for extended darkness and cold if the impact was large (1 km+)

Food & Water in an Impact Winter

An impact winter creates the same fundamental challenge as nuclear winter: how do you feed people when agriculture is impossible?

Water

• Rainwater is unsafe in the initial months — acid rain contamination from sulfuric and nitric acid. pH can drop to 2–3, comparable to vinegar.
• Groundwater and deep wells remain the safest sources. Springs fed by deep aquifers are ideal.
• Surface water (rivers, lakes) will be contaminated by fallout debris, acid rain, and ash. Filtration and testing required.
• Snow and ice: Usable but must be filtered and tested for acidity. Boiling does not remove acid contamination — you need neutralization (e.g., small amounts of baking soda) or proper filtration.
• Minimum requirement: 3.5 liters per person per day for survival; 7+ liters when accounting for cooking and basic hygiene.

Food Production Under Reduced Sunlight

Short-term (0–6 months):

• Rely on stored food: canned goods, dried grains, legumes, freeze-dried meals
• Forage for surviving root vegetables — potatoes, carrots, turnips, and beets may survive underground even after surface vegetation dies
• Preserved food from any surviving stores, warehouses, or supply chains

Medium-term (6–24 months):

• Indoor/greenhouse growing: Cold-hardy, low-light crops can grow under artificial or filtered light. Prioritize:
  • Mushrooms (no sunlight needed — grow on dead organic matter)
  • Potatoes (low light tolerant, high caloric yield — roughly 17 million calories per hectare)
  • Kale, spinach, and other cold-hardy greens
  • Radishes and turnips (fast growing, cold tolerant)
  • Soybeans and lentils (protein-dense)
• Insect farming: Crickets and mealworms can be raised indoors on organic waste. They provide high-quality protein with minimal resource input — roughly 12x more feed-efficient than cattle.
• Fishing: Aquatic ecosystems collapse more slowly than terrestrial ones. Freshwater fishing may remain viable for 6–18 months after impact. Deep ocean fisheries may persist longer.

Long-term (2+ years):

• Seaweed and algae cultivation: Spirulina and chlorella can be grown in bioreactors with minimal light. These provide complete protein, essential fatty acids, and vitamins.
• Hydroponic systems: With any available power source (generators, solar panels — which still produce some output even under dust-dimmed skies, or wind/hydro), indoor food production becomes critical infrastructure.
• Caloric target: An adult needs roughly 2,000 calories per day for sedentary survival, 3,000+ for active work in cold conditions. Plan for 1,500 as an extended rationing minimum.

Long-Term Survival: Years of Reduced Sunlight

A large impact winter may last 2–10 years. Surviving it requires shifting from emergency mode to sustainable adaptation.

Energy

• Wood and biomass: Dead trees from firestorms provide fuel for years, but burning them adds particulates to already-polluted air. Use efficient stoves with good ventilation.
• Solar panels: Output drops 20–40% under a moderate dust veil, more under severe conditions. Still worthwhile, especially as skies gradually clear.
• Wind power: Unaffected by dust veil. Small wind turbines become extremely valuable.
• Hydroelectric: If river flows continue (likely, though reduced), micro-hydro is the most reliable power source.
• Fuel stores: Gasoline degrades in 6–12 months, diesel in 12–24 months with stabilizer. Prioritize fuel for critical tasks.

Shelter & Warmth

• Insulation is king. Retrofit existing structures: seal drafts, add insulation layers, create smaller heated zones within larger buildings.
• Target interior temperature: 10–15°C (50–59°F) is survivable with proper clothing. Heating an entire house to 20°C wastes fuel.
• Underground advantages: Below the frost line (1–2 meters in temperate zones), ground temperature stays relatively stable at 8–13°C year-round, even during an impact winter.
• Community consolidation: Multiple families sharing one well-insulated structure is far more efficient than heating separate homes.

Health Challenges

• Vitamin D deficiency: Without adequate sunlight, widespread deficiency develops within 2–3 months. Symptoms: bone pain, muscle weakness, depression, immune suppression. Stockpile supplements or consume fatty fish, egg yolks, and liver.
• Respiratory illness: Particulate-laden air causes chronic respiratory problems. N95 or P100 masks for outdoor activity. HEPA filtration for shelter ventilation.
• Mental health: Extended darkness, isolation, grief, and uncertainty create severe psychological stress. Maintain routines, social connection, and purpose. This is not optional — psychological collapse kills communities.
• UV exposure (post-dust clearing): When the dust veil thins, depleted ozone means extreme UV levels. Sunburn in minutes. Skin cancer risk spikes. Wear UV-protective clothing and eyewear outdoors.

Community Rebuilding

Individual survival in an impact winter is nearly impossible beyond a few months. Community is not a luxury — it’s a survival requirement.

Immediate Organization (Week 1–4)

• Inventory skills: Medical personnel, engineers, farmers, mechanics, teachers, hunters — every skill matters.
• Inventory resources: Pool food, water, fuel, tools, medications, seeds, and equipment.
• Establish governance: Even minimal structure — a rotating council, assigned roles, conflict resolution process — prevents the chaos that kills more people than the disaster itself.
• Security: Desperate people do desperate things. Establish watches and secure critical resources without creating a fortress mentality that alienates potential allies.

Medium-Term Structure (Month 1–12)

• Food production teams: Dedicated groups managing greenhouses, mushroom cultivation, foraging, fishing, and food preservation.
• Medical corps: Organize available medical knowledge and supplies. Train basic first aid widely.
• Infrastructure maintenance: Water systems, sanitation, power generation, shelter repairs.
• Education: Don’t stop teaching children. Knowledge preservation is civilization preservation.
• Communication: Establish contact with other surviving communities. HAM radio operators become critically important.

Long-Term Recovery (Year 1+)

• Seed banking: Protect seed stocks above all else. Seeds are the bridge to agricultural recovery.
• Selective outdoor planting: As dust clears (even partially), begin test plots with cold-hardy, fast-maturing crops.
• Record keeping: Document everything — weather patterns, crop results, medical observations, community decisions. This data is invaluable for recovery.
• Trade networks: As contact with other communities develops, establish trade. Specialization and exchange accelerate recovery.

Planetary Defense: What’s Being Done

Humanity is not helpless against asteroid impacts. For the first time in Earth’s history, a species has the technology to detect and potentially prevent a cosmic impact.

Detection

• Current catalog: Over 34,000 known near-Earth asteroids as of 2025. Roughly 2,500 are classified as potentially hazardous (>140 m diameter, orbits within 7.5 million km of Earth).
• NEO Surveyor: NASA’s dedicated infrared space telescope, designed to find 90%+ of potentially hazardous NEOs. Operational from 2028.
• Vera C. Rubin Observatory: Ground-based telescope in Chile, capable of discovering thousands of new NEOs annually starting 2025.
• International Asteroid Warning Network (IAWN): Coordinates global detection and tracking efforts.

Deflection

• DART Mission (2022): NASA’s Double Asteroid Redirection Test successfully altered the orbit of asteroid Dimorphos by crashing a spacecraft into it at 6.6 km/s. The impact changed the asteroid’s orbital period by 33 minutes — far exceeding the minimum benchmark of 73 seconds. Proof of concept: kinetic impactor deflection works.
• ESA’s Hera Mission (2024): Follow-up mission to study the DART impact site in detail, refining our understanding of kinetic deflection.
• Kinetic impactor: Ram a spacecraft into the asteroid at high speed. Most effective with years to decades of warning. A small velocity change years before impact translates to a miss distance of thousands of kilometers.
• Gravity tractor: Station a massive spacecraft near the asteroid for months or years. Gravitational attraction slowly alters the asteroid’s trajectory. Best for smaller asteroids and long lead times.
• Nuclear standoff detonation: For large asteroids with short warning times. A nuclear device detonated near (not on) the asteroid surface vaporizes a layer of material, creating a jet of debris that pushes the asteroid off course. This is the only current option for large asteroids with less than ~10 years warning.
• Ion beam deflection: A spacecraft directs an ion engine’s thrust at the asteroid surface. Slow but continuous force. Still theoretical at scale.

What You Can Do

• Support planetary defense funding. NASA’s entire planetary defense budget is roughly $200 million/year — less than the cost of a single Hollywood disaster movie.
• Follow the B612 Foundation (b612foundation.org) — a nonprofit dedicated to protecting Earth from asteroid impacts.
• Stay informed: NASA’s CNEOS (Center for Near Earth Object Studies) publishes real-time close-approach data at cneos.jpl.nasa.gov.

Gear Checklist: Asteroid Impact Preparedness

This checklist overlaps significantly with nuclear winter preparedness. Focus on long-duration, cold-weather, low-infrastructure survival.

Tier 1: Immediate Survival (Bug-Out / 72-Hour Kit)

• N95/P100 respirator masks (minimum 50 per person)
• Safety goggles (sealed, anti-fog)
• Emergency radio (hand-crank/solar, AM/FM/NOAA weather)
• Headlamp + spare batteries (lithium — longer shelf life)
• First aid kit (comprehensive, including trauma supplies)
• Water: 1 gallon per person per day × 3 days minimum
• Water purification: filter (0.1 micron+), purification tablets, UV pen
• Food: 72 hours of calorie-dense, no-cook meals
• Emergency blankets, sleeping bag (rated to -20°C / -4°F)
• Multi-tool, fixed-blade knife
• Fire-starting kit (ferrocerium rod, waterproof matches, lighters)
• Duct tape, plastic sheeting (for sealing shelter)
• Cash (small bills — ATMs won’t work)
• Copies of important documents in waterproof bag

Tier 2: Extended Survival (2 Weeks to 3 Months)

• Stored food: canned goods, rice, beans, lentils, oats, honey, salt, cooking oil (target 2,000 cal/person/day)
• Large water storage (55-gallon drums, WaterBOBs for bathtub)
• Water testing kit (pH strips minimum — for acid rain detection)
• Baking soda (water neutralization, cleaning, cooking)
• Wood-burning stove or rocket stove + fuel supply
• HEPA air purifier (or DIY: box fan + MERV-13 filter)
• Vitamin D supplements (5,000 IU/day per adult)
• Full-spectrum multivitamins
• Prescription medications (90-day supply minimum)
• HAM radio (with license and practice using it before disaster)
• Solar panel (portable, 100W+) + charge controller + battery bank
• LED grow lights + timer
• Heirloom seed collection (non-GMO, open-pollinated — you need seeds that produce viable next-generation seeds)

Tier 3: Long-Duration Resilience (3 Months to Years)

• Greenhouse materials (polycarbonate panels, PVC frame supplies, or pre-fab greenhouse kit)
• Mushroom spawn (oyster mushrooms are the easiest and most productive)
• Insect farming starter kit (cricket or mealworm)
• Spirulina/chlorella culture starter
• Hand tools for agriculture (shovel, hoe, rake, wheelbarrow)
• Comprehensive seed library with growing guides
• Books: agriculture, medicine, engineering, repair — physical copies (digital may be inaccessible)
• Wind turbine (small, 400W+) for consistent power through dust veil
• Micro-hydro generator (if near flowing water)
• Geiger counter / dosimeter (impact events can disturb nuclear facilities)
• Sewing kit, fabric, leather-working tools (clothing manufacture and repair)
• Barter goods: alcohol, tobacco, coffee, ammunition, salt, soap

Final Thoughts

An asteroid impact large enough to threaten civilization is, statistically, the least likely apocalyptic scenario you’ll face in your lifetime. But it’s also one of the few we can see coming — and one of the only ones we can prevent entirely with sufficient investment in planetary defense.

The Chicxulub asteroid ended the reign of the dinosaurs. They had no space program. You do.

The most important thing you can do about asteroid impacts isn’t building a bunker — it’s supporting the detection and deflection infrastructure that ensures we never need one. But if the worst happens, the physics of impact winter are survivable. Humanity endured the Toba supervolcanic eruption roughly 74,000 years ago — a comparable climate catastrophe — with Stone Age technology.

You have better tools. Use them.