Call it "close encounters of the cosmic kind."
On Friday - the same day a meteor exploded over Russia's Ural Mountains, injuring nearly 1,000 people - an asteroid passed by the Earth, the closest encounter NASA has seen for an object of that size.
The asteroid, which is known as 2012 DA14, passed at 2:24 p.m. EST, but it was too small to be seen by the naked human eye.
The asteroid is thought to be about 150 feet long, or half the size of a football field. Astronomers had projected it to come as close as 17,100 miles from the surface of the Earth.
That's closer than the weather and communication satellites that ring our planet at about 22,300 miles above the Earth, and much closer than the moon, which is about a quarter-million miles away.
NASA Scientists: Keep calm, carry on
But scientists with NASA's Jet Propulsion Laboratory say people have nothing to worry about, as it is impossible for the asteroid to hit the planet.
"There is no chance that the asteroid might be on a collision course with Earth," the agency wrote on its site.
- Read More: NASA's Earth Flyby Reality Check
Scientists say there are millions of asteroids in the solar system, with the majority of them hanging out in the asteroid belt between the orbits of Mars and Jupiter.
It's not uncommon for an asteroid to actually enter the Earth's atmosphere - in fact, scientists say about 100 tons of rocks come into the Earth's atmosphere every day. However, most of them are small and they explode in the upper levels of the atmosphere, their remnants vaporizing before they ever reach the other.
Some of those asteroids are, like 2012 DA14, categorized as "Near-Earth asteroids," which are asteroids with orbits that pass near that of Earth. As of Feb. 2, 2013, NASA scientists had estimated that there were about 9,604 such asteroids.
More than 1,300 of those have been categorized as "potentially hazardous," which means they may someday come close to or hit Earth. NASA monitors these asteroids, and right now they say there are no eminent threats.
Asteroid events in recent history
Such an event has happened before, in 1908, when an asteroid entered the atmosphere over Tunguska, Russia, and exploded, but again, scientists stress that impact is not possible for this asteroid.
Scientists say that an event like the asteroid that exploded over Tunguska, which is estimated to have been between 45-70 meters, is likely to happen once every couple thousand years.
Scientists at NASA's Near-Earth Object program at California's Jet Propulsion Laboratory estimate that an object of this size makes a close approach like this every 40 years. The likelihood of a strike is every 1,200 years.
Several other asteroid "events" have been reported in recent years, including a large fireball that was observed over the skies in Indonesia in October 2009 and a collision that occurred over the Mediterranean Sea in June 2002. In addition, scientists calculated that a small asteroid would hit the Earth over the Sudan in October 2008.
The asteroid hit as predicted, making it the first time scientists had been able to accurately predict an asteroid impact.