A truly exceptional event occured on the night of November 13, 1833: a myriad of lights seemed to fall from the sky, thick like snow, and so much so that many people believed that the stars had really fallen and were afraid that none would appear the next night. Naturally, the stars had nothing to do with it and the next night, they were still in the same place. This phenomenon, though very special and impressive, is not very rare: if we get far enough away from the lights of the city, on any clear night we can observe from 10 to 20 "shooting stars" every hour. These are fragments of rock and metal, sometimes no larger than a pebble, which come mainly from the asteroid belt. Penetrating into the Earth's atmosphere at a speed of between 100 and 300 000 kilometers per hour, they begin to burn due to the heat generated by friction, leaving behind a fiery wake that has been called a meteor. During this flight, the fragments often disintegrate before reaching the ground, but sometimes they are large enough to avoid complete destruction and thus become those objects we call meteorites. Every day, about twenty tons of cosmic material, consisting mainly of dust, is added to the Earth's mass; however, scientists are much more interested in the larger meteorites: the study of these objects, which formed during the same period in which the planets were born, is in fact of fundamental importance to determine their original composition. Most of the meteorites found on Earth are composed of rock. The metal types are much more rare while there are others that are a mix of the the two. Rocky meteorites are composed mainly of siliceous rock with traces of iron and nickel; the metallic types consist almost exclusively of a mix of iron and nickel. Naturally, the former, once they reach the ground, are more difficult to recognize because they tend to change much more rapidly on the surface, due to contact with the air and water, than the metallic types. The largest meteorite ever found was discovered in Namibia (where it is still located) in 1920 and weighs approximately 60 tons. The second largest weighs half as much and is on display in the Museum of Natural History in New York.
A truly exceptional event occured on the night of November 13, 1833: a myriad of lights seemed to fall from the sky, thick like snow, and so much so that many people believed that the stars had really fallen and were afraid that none would appear the next night. Naturally, the stars had nothing to do with it and the next night, they were still in the same place. This phenomenon, though very special and impressive, is not very rare: if we get far enough away from the lights of the city, on any clear night we can observe from 10 to 20 "shooting stars" every hour. These are fragments of rock and metal, sometimes no larger than a pebble, which come mainly from the asteroid belt. Penetrating into the Earth's atmosphere at a speed of between 100 and 300 000 kilometers per hour, they begin to burn due to the heat generated by friction, leaving behind a fiery wake that has been called a meteor. During this flight, the fragments often disintegrate before reaching the ground, but sometimes they are large enough to avoid complete destruction and thus become those objects we call meteorites. Every day, about twenty tons of cosmic material, consisting mainly of dust, is added to the Earth's mass; however, scientists are much more interested in the larger meteorites: the study of these objects, which formed during the same period in which the planets were born, is in fact of fundamental importance to determine their original composition. Most of the meteorites found on Earth are composed of rock. The metal types are much more rare while there are others that are a mix of the the two. Rocky meteorites are composed mainly of siliceous rock with traces of iron and nickel; the metallic types consist almost exclusively of a mix of iron and nickel. Naturally, the former, once they reach the ground, are more difficult to recognize because they tend to change much more rapidly on the surface, due to contact with the air and water, than the metallic types. The largest meteorite ever found was discovered in Namibia (where it is still located) in 1920 and weighs approximately 60 tons. The second largest weighs half as much and is on display in the Museum of Natural History in New York.
