A look at the heavenly bodies and the danger they may pose for our planet

Berlin AP

What is the difference between a meteor and a meteorite? Meteors are pieces of space rock, usually from larger comets or asteroids, that enter the Earth’s atmosphere. Many are burned up by the friction and heat, but those that survive and strike the Earth are called meteorites. They often hit the ground at speeds of up to 30,000 kph, releasing a huge amount of energy, according to the European Space Agency (ESA).

How common are meteor strikes? Experts say that smaller strikes happen five to 10 times a year. Large meteors such as Friday’s in Russia are rarer, but still occur roughly every five years. Most of them fall over uninhabited areas where they do not injure humans.

How big was Friday’s bang in Russia, and why did it cause so many injuries? Most of the damage would have been caused by the blast — or blasts — as the meteor broke up in the atmosphere. Its rapid deceleration released a huge amount of energy that would have been heard and felt many kilometers away. Witnesses say it shattered windows and sent loose objects flying through the air.

While estimates of the meteor’s mass range from 10 to 100 tons and it is still unclear if it consisted of rock or iron, “the explosive force of the airburst might have been some 10 kilotons of TNT,” said Alan Harris, a senior scientist at the German Aerospace Center. But he noted that since the blast occurred several kilometers above Earth, the damage is not comparable to an explosion of that magnitude on the planet’s surface. By comparison, the atomic bomb dropped on Hiroshima in 1945 had an explosive force of about 15 kilotons, but it detonated just 700 meters above the densely populated city.

Is there any link between this meteor and the asteroid flyby later Friday? No, it is just coincidence, according to ESA spokesman Bernhard von Weyhe, who said Asteroid 2012 DA14 is unrelated to the meteor strike in Russia.

When was the last comparable meteor strike? In 2008, astronomers spotted a meteor similar to the one in Russia heading toward Earth around 20 hours before it entered the atmosphere. It exploded over the vast African nation of Sudan, causing no known injuries.

The largest known meteor in recent times caused the 1908 Tunguska event, flattening thousands of square kilometers of forest in remote Siberia. Nobody was injured by the blast, nor by the Sikhote-Alin meteor that fell in eastern Siberia in 1947.

Scientists believe that a far larger meteor strike on Mexico’s Yucatan Peninsula may have been responsible for the extinction of the dinosaurs about 66 million years ago. According to that theory, the meteor’s impact would have thrown up vast amounts of dust that blanketed the sky for decades and altered the climate on Earth.

What can scientists learn from Friday’s strike? Addi Bischoff, a mineralogist at Germany’s University of Muenster, said scientists and treasure hunters are probably already racing to find pieces of the meteorite. Some meteorites can be highly valuable, fetching up to $670 per gram depending on their origin and composition.

Because meteors have remained largely unchanged for billions of years, unlike rocks on Earth that have been affected by erosion and volcanic outbreaks, scientists study the fragments to learn more about the origins of our solar system.

Harris of the German Aerospace Center said some meteors are also believed to carry organic material and may have influenced the development of life on Earth.

What would happen if a meteor hit a major city? Scientists hope never to find out, but they have been trying to prepare for such an event anyway. The ESA’s von Weyhe said experts from Europe, the U.S. and Russia are already discussing how to spot potential threats sooner and avert them.

But don’t expect a Hollywood-style mission to fly a nuclear bomb into space and blow up the asteroid. “It’s a global challenge and we need to find a solution together,” von Weyhe said. “But one thing’s for sure — the Bruce Willis ‘Armageddon’ method won’t work.”