Hazards: Impacts in our future?

  • Collection Information

    • Thousands of asteroids and comets cross paths with earth. How dangerous are they?

      The great majority of asteroids orbit the Sun in well-ordered bands between Mars and Jupiter. But occasionally, a collision between two asteroids followed by a gravitational nudge from Jupiter shifts an asteroid into a new orbit that crosses paths with Earth.

      Fortunately, the largest and potentially most destructive asteroids-measuring several miles across-are extremely rare. Astronomers have already spotted most of them, and so far none poses a serious threat. But many thousands of asteroids, each as wide as a sports stadium, remain undiscovered. Although the odds of one striking any particular place are exceedingly small, such an impact could ruin a large metropolitan area.

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  • For Educators

    • Topic: Astronomy

      Subtopic: Milky Way Galaxy

      Keywords: Asteroid belt, Astrophysics, Asteroids--Collisions with Earth, Astrogeology, Collisions (Astrophysics), Near-Earth asteroids, Natural disasters

      Audience: General

In This Section

Global catastrophe

Global catastrophe

Asteroids large enough to cause widespread extinctions collide with Earth very rarely.

Gigantic tsunami

Gigantic tsunami

An asteroid with a diameter of one kilometer (0.6 mile) could completely devastate a land area the size of Europe and blanket Earth with dust.

Regional destruction

Regional destruction

Less damaging but more numerous are the asteroids with Earth-crossing orbits that are roughly 200 meters (660 feet) across, the size of a large sports stadium.

Large midair explosion

Large midair explosion

Asteroids the size of a 10-story building, 30 meters (100 feet) across, are about the smallest that can cause significant damage.

Small fireball

Small fireball

Every year U.S. military satellites detect about a dozen small asteroid explosions in the atmosphere. 

Protecting the planet

Protecting the planet

In the unlikely event that astronomers discovered a civilization-ending asteroid or comet destined to impact Earth in a month, we wouldn't have enough time to stop it.

Wild-card comets

Wild-card comets

Comets—clumps of ice and rock—come near Earth much less frequently than asteroids, but they travel much faster—one hundred times the speed of sound on Earth.