NASA's top planetary defense expert reveals the biggest threat isn't Hollywood-style doomsday rocks, but undiscovered ...

A NASA planetary defense officer warns thousands of near-Earth asteroids capable of destroying a city remain undetected.

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Orbiting between Mars and Jupiter is an enormous ring of space rocks. The region, known as the asteroid belt, is home to an estimated 1.9 million asteroids that are larger than 1 kilometer in diameter ...

Forgot what science-fiction has told you, flying through an asteroid belt would be a major challenge for anyone.

The object is hurtling towards the Earth at a zippy 12,616 miles per hour, according to data from the space agency.

If an asteroid is on a collision course with the moon, what should humanity do? Try to nudge the space rock out of the way before it strikes? Obliterate it with a nuclear explosion? Such a cosmic ...