Is there any link between this meteor and the larger asteroid that passed Earth later on Friday?
No, it's just cosmic coincidence. According to NASA, the trajectory of the Russian meteorite was significantly different from that of asteroid 2012 DA14. "In videos of the meteor, it is seen to pass from left to right in front of the rising sun, which means it was traveling from north to south. Asteroid DA14's trajectory is in the opposite direction, from south to north," the U.S. space agency said.
How often do meteorites hit Earth?
Experts say smaller strikes happen five to 10 times a year. Large meteors such as the one in Russia on Friday are rarer, but still occur about every five years, according to Addi Bischoff, a mineralogist at the University of Muenster in Germany. Most of them fall over uninhabited areas where they don't injure humans.
When was the last event like this?
In 2008, astronomers spotted a meteor similar to the one in Russia heading toward Earth about 20 hours before it entered the atmosphere. It exploded over the vast African nation of Sudan, causing no known injuries.
What would happen if a sizable meteorite hit a city?
A blast at low altitude or on the surface would result in many casualties and cause serious damage to buildings. The exact extent would depend on the mass of the meteorite, its speed and composition. European Space Agency spokesman Bernhard von Weyhe says experts from Europe, the U.S. and Russia are working on way to spot potential threats sooner and avert them. But don't expect a Hollywood-style mission to fly a nuclear bomb into space, like the movie Armageddon.