Meteorites are natural objects that originate in outer space and survive contact with the earth's surface. When they are still in space, they are known as meteoroids. However, as they enter earth's atmosphere, their outer surface burns, due to the outer impact pressure. With this, they start resembling a fireball and are known as a meteor or meteorite or shooting star. In effect, meteorites can also be termed as natural objects that are found on the surface of a celestial body and come from elsewhere in space. These meteorites have been classified into different categories, as per their different characteristics. Read on to know about the varied kinds of Meteorites.
Different Types of Meteorites
As per popular belief, when asteroids melted, iron - being a denser metal, sank down to the centre, to form a metallic core. In effect, most iron meteorites are considered to be the cores of asteroids. The composition of an iron meteorite mainly includes iron-nickel metal alloy. It has a distinctive crystalline structure, containing bands of varying - low and high levels of nickel, known as Widmanstatten texture.
The low nickel alloy in an iron meteorite is the mineral kamacite and the high nickel alloy is taenite. They resemble the terrestrial minerals - ferrite and austite. Moreover, a wide variation in the texture as well as the mix of other minerals is seen within iron meteorites, such as iron sulphides and iron carbides. This implies that there are a lot of different groups and sub-types of iron meteorites, which can be related to both stony achondritic and chondrite meteorites.
Stony Iron Meteorites
Stony iron meteorites are amongst the rarest and most beautiful of all meteorites. They consist of equal amounts of iron-nickel metal and silicate minerals. With this, it becomes difficult to decipher, when a silicate iron becomes a stony-iron. There are two kinds of stony iron meteorites, namely mesosiderites, and pallasites. Mesosiderites are a collection of stone and metal, while pallasites, contain nickel-iron, intermingled with large crystals of olivine, a yellow-green igneous rock that is translucent in thin slices or polished tones. This makes them the most beautiful of all meteorites that exist.
Though stony meteorites are the most common, they are also the most precious and valuable, as they are hard to distinguish from earth rocks. Moreover, they are comparatively vulnerable, as they erode more quickly than the durable irons and stony-irons. They are quite varied in structure and content and are divided into two main categories - chondrites and achondrites. Chondrites contain chondrules, which are microscopic to marble-sized, spherical globs of silicates, belonging from the earliest solar nebula, sometimes pre-dating even planetary formation. On the other hand, Achondritic meteorites are pieces of other mature planets or moons, which were ejected by a large impact and may have traveled the solar system for eons, before landing on earth.