At least 1,000 people have been injured in Russia as the result of a meteor exploding in the air. The energy of the detonation appears to be equivalent to about 300 kilotons of TNT, said Margaret Campbell-Brown of the department of physics and astronomy at the University of Western Ontario.
Meanwhile, an asteroid approached Earth but did not hit it, coming closest at about 2:25 p.m. ET.
You probably have some questions about both of those events, so here's a brief overview:
1. Are these events connected?
The meteor in Russia and the asteroid that passed by on Friday afternoon are "completely unrelated," according to NASA. The trajectory of the meteor differs substantially from that of asteroid 2012 DA14, NASA said. Estimates on the meteor's size are preliminary, but it appeared to be about one-third the size of 2012 DA14.
The term "asteroid" can also be used to describe the rock that exploded over Russia, according to the European Space Agency and NASA, although it was a relatively small one.
2. What's the difference between an asteroid and a meteorite and other space rocks?
According to NASA, here's how you tell what kind of object is falling from the sky:
Asteroids are relatively small, inactive rocky bodies that orbit the sun.
Comets are also relatively small and have ice on them that can vaporize in sunlight. This process forms an atmosphere and dust and gas; you might also see a "tail' of dust or gas.
Meteoroids are small particles from comets or asteroids, orbiting the sun.
Meteors are meteoroids that enter the Earth's atmosphere and vaporize, also known as shooting stars.
Meteorites are meteoroids that actually land on the Earth's surface. The pieces of the meteor that exploded in Russia are meteorites.
Generally meteorites are smaller than grains of sand and vaporize on passage through the atmosphere. But there are also larger meteorites.
Comets and asteroids are left over from when the solar system formed. There used to be more of them, but over time they've collided to form major planets, or they've got booted from the inner solar system to the Oort cloud or have been ejected from the solar system entirely.
3. Why didn't we see the Russian meteor coming?
Only one space rock that impacted the planet has ever been observed before it hit the Earth, Campbell-Brown said.
That's because objects that do hit the Earth tend to be smaller, and it's too hard to see them. The one sighting before impact happened in 2008, a day before a meteor exploded over Sudan.
Current estimates suggest that the Russian meteor was about 15 meters (49 feet) across, which is too small for telescopic surveys.
"Unfortunately the objects of this size have to be very close to Earth for us to be able to see them at all," Campbell-Brown said.
The asteroid that approached Earth today, which NASA has been tracking, is about 45 meters long, which is relatively small for an asteroid.
4. How does this compare to other Earth impacts?
The Earth picks up tons of meteoric debris every day, but big pieces are fairly uncommon, said David Dundee, astronomer at Tellus Science Museum in Cartersville, Georgia.
An object the size of the Russian meteor comes in about once every 50 years, but none has been recorded since 1908, when an asteroid exploded and leveled trees over an area of 820 square miles - about two-thirds the size of Rhode Island - in Tunguska, Russia.
"This is the largest event that we know of that's happened since Tunguska," Campbell-Brown said.