Particles (known as meteoroids) that come from interplanetary space, on the other hand, are natural.

ECONOMIST: Orbital debris

Cooke says Earth was pelted by meteoroids at about the same time, but they hit the moon because it has no atmosphere to protect it.

CNN: Bright explosion on moon visible from Earth, NASA says

That's still big enough potentially to produce meteorites -- which are meteoroids, or fragments thereof, that do manage to hit the Earth -- before burning completely.

CNN: Meteor lights up East Coast -- and social media

According to the U.S. National Aeronautics and Space Administration, meteoroids smaller than 25 meters usually burn up as they streak through the atmosphere, causing little or no damage.

WSJ: Meteorite Hits Russia, Causing Panic

In 1997, the US National Research Council said that Nasa should carry out a thorough risk assessment to determine the likelihood that the space shuttle could be severely damaged by meteoroids and orbital debris.

BBC: Was Columbia struck by space debris?

Some satellite developers are beginning to design spacecraft so that sensitive instruments are located towards the back of the satellite to minimise any risk of impact damage, and the side facing away from earth is shielded to protect it from meteoroids.

ECONOMIST: Orbital debris