Iron meteorites have long fascinated astronomers and scientists due to their magnetic properties. While the magnetism in these meteorites is not particularly strong, it holds valuable information about their origin and formation. Contrary to popular belief, using magnets to distinguish meteorites from surrounding rocks can actually erase the magnetic history of these celestial objects, which is essential for scientific research and understanding.
The magnetism in meteorites is a result of their formation in the presence of a magnetic field. The alignment of iron grains within the meteorite along the external magnetic field gives the meteorite its own magnetism. For instance, the Martian meteorite named “Black Beauty” acquired its magnetism from the strong magnetic field of a young Mars.
Magnetism in Unexpected Cases
Interestingly, some meteorites that shouldn’t have formed in a strong magnetic field exhibit magnetic properties. Iron meteorites are typically classified based on their chemical composition, particularly the ratio of nickel to iron. One category, known as IVA, is believed to be fragments of smaller asteroids. As these small asteroids lack strong magnetic fields, IVA meteorites are not expected to be magnetic. However, recent studies show otherwise.
The Puzzle of Small Asteroids
Small asteroids are formed through a process called the “rubble pile method”, where chunks of iron-rich rock gradually aggregate over time to form an asteroid. These bodies do not generate strong magnetic fields, as they lack the presence of liquid iron needed for a dynamo effect. This raises the question: how do some small asteroids possess magnetism?
The Role of Collisions
Asteroids are exposed to countless collisions throughout their existence. These collisions result in the formation of fragments that eventually become meteorites found on Earth. The new study shows that these collisions can create a magnetic dynamo within an asteroid.
If a colliding body is not large enough to shatter the asteroid but can melt a layer of material near the surface, a chain of events unfolds. The cold rubble core heats up when surrounded by a molten layer. As lighter elements evaporate from the core and migrate towards the surface, convection is generated, which churns the layers. This convection of iron generates a magnetic field, leaving magnetic imprints on certain parts of the asteroid. Subsequent collisions then lead to the creation of magnetic fragments, some of which reach Earth as meteorites.
Implications for Solar System History
Understanding the magnetism of IVA meteorites sheds light on the history of our solar system and the occurrence of asteroid collisions. It provides insights into events such as planetary drift, which may have triggered more frequent collisions among asteroids. This knowledge allows researchers to reconstruct and analyze the complex interplay of celestial bodies within our solar system, leading to a more comprehensive understanding of its evolution.
The discovery of meteorites is an exciting endeavor, but it is essential to approach it with caution. The use of hand magnets can not only erase the magnetic history of these extraordinary celestial objects but also unintentionally alter valuable scientific records. It is crucial to handle meteorites with care to preserve their magnetic integrity and retain the information they hold about our solar system’s past.
Iron meteorites, with their intriguing magnetic properties, offer valuable insights into the formation and history of asteroids and our solar system as a whole. While their magnetism may seem relatively weak, it holds significant scientific value. The unexpected magnetism found in some meteorites adds another layer of complexity to our understanding of these cosmic bodies. By unraveling the mysteries behind the magnetism of iron meteorites, researchers can continue to unlock the secrets of our solar system’s past and gain a deeper appreciation for the dynamic nature of the universe.
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