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Iron meteorites, although they are the most recognizable to the untrained eye, are only about 18 times less abundant than stony meteorites. Being composed primarily of iron (usually with nickel), they are heavier than ordinary rocks and normally appear a very dark reddish-brown or black. Their surfaces, while irregular, may have a smoothed-over feel caused by melting on the way through the atmosphere. However, the surface of just-discovered iron meteorites may be crusted and rusty due to oxidation, perhaps due to lying on or near the surface for millennia after falling. Many iron meteorites also exhibit characteristic scalloped or thumbprint-shaped markings known as regmaglypts. These may form through ablation as the heated body passes through the atmosphere. The large hole in this sample likely is the result of the same kind of forces that form the regmaglypts, except in this case it went completely through the body. Image courtesy of NASA. |