The meteorites are pieces of other bodies in our solar system that fall to Earth when a meteor , or a “falling star” shines through our atmosphere at speeds between 15 and 70 kilometers per second. Most of them originate from asteroid impacts with other asteroids. Some come from the Moon and, perhaps, from comets and Mars. Meteorites that are found after a meteor event has been observed are called “falls”, while those that are found by chance are called “finds”. The name of meteorites generally derives from the locality or geographic formation closest to the place of discovery. The term “meteorite”
Meteorite matter contains some of the rarest elements on Earth, far rarer than gold, and shows us what the composition of our planet must have been like at the time of its formation. Due to their rarity and primeval origins, meteorites are sought after by scientists as well as collectors.
There are three major classes of meteorites: rocky , ferrous, and rocky-ferrous .
The rocky meteorites are divided into two groups: chondrites and meteorites . Most chondrites have remained unchanged since their formation, which occurred 4,56 billion years ago, that is, shortly after the formation of the Sun. Almost all chondrites contain chondrules – small inclusions gaseous spherical shape that are formed at the time of solar nebula
Achondrites appear to have been chondritic in nature before being altered by heat or some impact. Achondrites are much rarer than chondrites and include the group of meteorites from the asteroid Vesta (HED) and the planet Mars (CNS).
The iron meteorites are believed to be pieces of crushed nuclei of asteroids differentiated and shall contain amounts of nickel variables. This class is divided into three basic groups: hexahedrites , with 4.5% – 6.5% nickel, octahedrites , with 6.5% – 13% nickel and ataxites , with 16% – 30% nickel . From the point of view of weight, ferrous meteorites are the most relevant class.
Mesosiderites and pallasites are the two main groups of iron-rock meteorites . Mesosiderites are angular fragments of rock and nickel-iron that have fused together due to impact with another body. Pallasites, one of the most fascinating meteorites, are believed to have formed on the boundary between the core and the mantle of asteroids: they contain olivine (peridot) crystals.
What are shooting stars or meteors?
The shooting stars (or meteors , which is the same) are small particles (usually between one millimeter and several centimeters) that entering at high speed in the Earth ‘s atmosphere is “burned” by friction (actually the brightness due to the ionization of the air around them) and produce the luminous trace that quickly crosses the sky and that we call a shooting star.
Its appearance is very varied. They can shine a lot or a little. Its trajectory can be short or long. Some may leave a trail for a few moments and others may not. They are usually quite fast (they disappear before we have time to say it!) But there are also slow ones, which can last several seconds. Sometimes they can show some color: reddish, greenish, bluish, etc. according to the chemical composition of the meteor.
The origin of these particles is in comets , which in their path are losing material and leaving it behind.
If the particle is large (a few centimeters), the meteor will be very bright and is called a fireball . What we see glowing is the ball of ionized air that surrounds them. Racing cars can be spectacular for their brightness, which can make them look even during the day. Some can fragment during their trajectory, present flashes or small explosions, or make noise. They often leave a persistent trail for a few moments (it’s the trail of ionized air they leave behind), or a trail of smoke. Sometimes they can be bright enough to be seen behind the clouds, and then we will see the clouds light up for a few moments.
Meteors or shooting stars can be observed on any clear night, although on certain nights of the year they are more abundant ( meteor showers ). See more about how to observe the Perseids and other meteor showers.
Atmospheric friction is capable of burning meteors weighing up to several kilos . However, if a particle is too large, it may not fully disintegrate and reach the Earth’s surface . The meteor is then called a meteorite . Our planet is constantly receiving meteorites of microscopic size and larger.
