More than 1 mile (2 km) wideThe space rock, dubbed 2006 VV2, came within 2.1million miles of hitting us - which is a near miss in space terms, even though that's about nine times farther away than the moon.
The asteroid was flying past Earth on Friday night, at 11 p.m. (PDT), and on Saturday 7 a.m. GMT for Europe.
There was no danger of collision. And that's a really good thing. This space rock, named 2006 VV2, is more than a mile wide (about 2 kilometers), according to the Web site.
If one that big hit Earth, it would blow a crater the size of London and wipe out a whole country; it would derail global commerce and create a climate change unlike anything seen in modern history.
Jay Tate, who runs Spaceguard UK, said: "Asteroids are a very real danger. We need to find and track them. Dinosaurs are extinct because they couldn't do anything about the asteroid hazard. We face precisely the same risk."
The best viewing locations were in the Americas, as the rock passed directly over Southern California, and though it has been far too dim to see with the naked eye, amateur backyard astronomers were able to spot it with good-sized telescopes and CCD cameras.
But one asteroid called Apophis will pass very close to Earth in the year 2029 and has a minor chance of hitting the planet in 2036, though it will most likely come close to the earth.
In fact, this asteroid will be the first in human history to be clearly visible to the naked eye.
The asteroid is said to have the power of 65,000 Hiroshima bombs. Also, it has the power to wipe out a small country, and churn up a tidal wave that could become 800 ft (244 m) high. These are things that could happen if Apophis hits the earth.
As for now, with the little risk that the asteroid has to hit the Earth, NASA has decided to hold off on devising any plans until they can get a more accurate idea of what is in store for Apophis, the asteroid.