Global · Space
Asteroid Impact
WatchImpact by a near-Earth asteroid or comet large enough to cause regional or global destruction.
- Likelihood
- Very low per year; certain over geological time
- Impact
- Existential at large diameters
- Horizon
- Any time; centuries between serious events
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Background
What this actually is
NASA and partners have catalogued the large majority of near-Earth objects above 1 km — the size that would cause global effects — and none currently pose a threat this century. The gap is in the 50-150 m range, which is far more numerous and much harder to detect.
An object of that smaller size arriving over a city would destroy it. Tunguska in 1908 flattened 2,000 square kilometres of forest and was probably around 50 m. Chelyabinsk in 2013 injured 1,500 people and was detected only on arrival.
This is the only natural existential threat that is now partly solvable. NASA's DART mission successfully changed an asteroid's orbit in 2022, proving kinetic deflection works given enough warning time.
Aotearoa
What it means for New Zealand
An ocean impact anywhere in the South Pacific would generate tsunami along New Zealand's coastline. Otherwise NZ's exposure is the same as everywhere: an atmospheric or land impact would be a global climate and supply event. NZ hosts optical tracking infrastructure that contributes to international survey work.
Watch for
Early warning signs
- NASA Sentry or ESA risk list entries moving above Torino scale 1
- Planetary defence conference notifications
- Increasing close-approach counts are normal, not alarming — detection is improving
Action
How to prepare
- 01
Nothing at household level for the large-object case
- 02
Coastal tsunami readiness covers the realistic South Pacific impact scenario
- 03
Support the surveys — planetary defence is cheap relative to what it prevents
Go deeper
Where to find more information
In an emergency
New Zealand's official channels
- Get Ready — household preparedness
- Civil Defence / NEMA
- GeoNet — quakes, volcanoes, tsunami
- MetService severe weather warnings
In a life-threatening emergency call 111. RNZ National is New Zealand's designated lifeline broadcaster — keep a battery radio.
Connected
Related threats
Get prepared
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Preparing.nz is a practical guide for New Zealanders who want to be ready for the unexpected — earthquakes, storms, power cuts, pandemics and more.