The main difference between chondrites and achondrites is that chondrites are the oldest materials in the solar system whereas achondrites are materials from asteroids, Mars, and Moon.
Chondrites and achondrites are two types of stony meteorites containing mostly silicate materials. Generally, there are three types of meteorites; the other two types include iron meteorites and stony-iron meteorites. Meteorites are rock or metal that has fallen to the earth from outer space as a meteor.
Key Areas Covered
1. What are Chondrites
– Definition, Structure, Function
2. What are Achondrites
– Definition, Structure, Function
3. Similarities Between Chondrites and Achondrites
– Outline of Common Features
4. Difference Between Chondrites and Achondrites
– Comparison of Key Differences
Key Terms
Achondrites, Chondrites
What are Chondrites
Chondrites are stony meteorites with chondrules. They are primitive and pristine rocks in the solar system, originating over 4.5 billion years ago. They have never been melted. Chondrites are the most common type of meteorites that occur on the Earth. Although there are different types of chondrites, they share a very common feature: the presence of chondrules. In general, a chondrule is a round grain that occurs in the chondrites. Chondrules generally undergo melting before their accretion to the parent asteroids. More importantly, chondrites are the oldest solid materials in the solar system.
Figure 1: A Chondrite
Furthermore, chondrites did not undergo differentiation from the parent body. Chondrites form when various types of dust and smaller grains in the solar system come together to form primitive asteroids. Chondrules stuck together during the process of accretion. Therefore, metal occurs separately from the core and the mantle silicates. However, the process of melting destroys chondrules.
What are Achondrites
Achondrites are a type of stony meteorite with no chondrules. They come from asteroids, Mars, and the moon. However, they have melted into magma at some point. Generally, the cooling and the crystallization of magma form a concentric layered structure in a process known as igneous differentiation. In addition, this forms the rocky planets, including Earth, Mercury, Mars, and Venus forming planetary crusts, cores, and mantles. Therefore, achondrites give information about the formation and internal structure of the planets.
Figure 2: Achondrite
Moreover, achondrites do not contain chondrules due to the melting process it has undergone. Therefore, the differentiation process removes chondrules from stony meteorites. However, asteroids that are not big enough to undergo differentiation remain chondritic. Generally, there are four types of achondrites: the are primitive achondrites, asteroidal achondrites, lunar meteorites, and Martin meteorites.
Similarities Between Chondrites and Achondrites
- Chondrites and achondrites are two types of stony meteorites that contain different amounts of iron and nickel.
- Moreover, they are rocks or metals that have fallen to the earth from outer space as a meteor.
Difference Between Chondrites and Achondrites
Definition
Chondrites refer to a stony meteorite containing small mineral granules (chondrules), while achondrites refer to a stony meteorite without rounded grains.
Structure
Chondrites contain chondrules, while achondrites do not contain chondrules.
Occurrence
Moreover, chondrites are more common, while achondrites are less common.
Significance
Chondrites are the oldest materials in the solar system, while achondrites are materials from asteroids, Mars, and the Moon.
Melting and Differentiation
Chondrites did not undergo melting and differentiation, while achondrites underwent melting and differentiation.
Silica and Metals
Silica and metals occur separately in chondrites, while silica and metal occur together in achondrites.
Conclusion
In brief, chondrites and achondrites are the two types of stony meteorites that mainly contain silicate minerals. Generally, chondrites are the most common type of stony meteorite. They contain granules called chondrules. In addition, they are the oldest materials in the solar system. Generally, chondrites do not undergo differentiation. Therefore, silica and metal occur separately in chondrites. In comparison, achondrites are a less common type of chondrites that do not contain chondrules. However, achondrites are the materials from asteroids, Mars, and Moon. But achondrites have undergone differentiation. But, silica and metals occur together in achondrites. Therefore, the main difference between chondrites and achondrites is their occurrence.
References:
- Types of meteorites. Natural History Museum. (n.d.). Retrieved April 26, 2023.
Image Courtesy:
- “NWA869Meteorite” By H. Raab – Own work (CC BY SA-3.0) via Commons Wikimedia
- “MillbillillieMeteorite” By H. Raab – Own Work (CC BY-SA 3.0) via Commons Wikimedia
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