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Regmaglypts |
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Figure 1. Scale bar 1.5 cm. |
| Meteorite, Sikhote-Alin, Iron, IIAB |
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| Regmaglypts are
distinctive thumb-like depressions or pits that appear sculpted into the
surface of meteorites, most notably iron meteorites, though they occasionally
occur on stone meteorites as well. These features form during a meteoroid's
high-speed passage through Earth's atmosphere, where turbulent supersonic
airstreams shape the surface as the object decelerates. Historically, scientists thought regmaglypts resulted from the melting and disruption of low-temperature minerals, such as troilite or schreibersite, within the meteoroid. Today, however, it's widely understood that these depressions emerge due to intense atmospheric interactions during entry. As a meteoroid travels through the vacuum of space at speeds reaching tens of thousands of miles per hour, it encounters Earth's atmosphere and undergoes dramatic changes. Within minutes, the compression of air molecules ahead of it generates extreme friction and heat, raising the exterior temperature to as high as 3,000°F (1,650°C). Iron meteorites, primarily composed of minerals like kamacite, taenite, and lesser amounts of cohenite, schreibersite, and troilite, respond to these conditions based on their melting points: Kamacite: 1,500°C Taenite (with 30-40% nickel in solid solution): 1,460°C-1,470°C Cohenite (an iron carbide): 1,400°C Schreibersite (an iron-nickel phosphide): 1,000°C Troilite (an iron sulfide): 990°C Although graphite, with a melting point of 3,600°C, is present in trace amounts in iron meteorites, it plays a minimal role in this process. The lower melting points of minerals like troilite and schreibersite make them particularly susceptible to melting and ablation during atmospheric entry, contributing to the formation of regmaglypts. This journey through the atmosphere is a violent one, driven by extreme velocities and temperatures. Regmaglypts are a natural outcome of this dynamic process. Additional factors-such as ablation rates, atmospheric entry angle, velocity, duration of atmospheric exposure, tumbling, and the meteoroid's orientation-also influence their development and are critical considerations in studying these features. |
Figure 2. Scale bar 1.5 cm. |
| Meteorite, Gibeon, Iron, IVA |
| Regmaglypts |
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Figure 3. Scale bar 0.8 cm. |
| Meteorite, Pultusk, Stone, H5 chondrite |
| Regmaglypts |
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Figure 3. Scale bar 0.9 cm. |
| Meteorite, Sikhote-Alin, IIAB, Iron, IIAB |
| Regmaglypts |
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