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| Primary and Secondary Structures in Meteorites |
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| Directory | ||
| Listing of Structures |
| What this site is about, a brief preface: |
| Meteorites: The Physical Evidence
Over the last two centuries, the perception of meteorites has evolved dramatically. Before the early 1800s, these objects were dismissed as unusual rocks that didn't fit into the geological classifications of the day. They were often overlooked and relegated to the background of museum collections, far from the spotlight of scientific inquiry. Today, with increased curiosity and advanced study of their interiors, meteorites are recognized for their unique chemistry and structures, standing alone as the only pristine physical evidence we possess from over 4.56 billion years ago. The Original Blueprint: Primary Structures Primary structures in meteorites are the original features formed during their initial creation, which occurred billions of years ago in the solar nebula or on their parent bodies, such as asteroids or planets. These features are the meteorite's "birthmarks," preserved from subsequent in-space events. For example, chondrules--small, round grains found in chondritic meteorites- are believed now to have condensed from gas and dust in the solar nebula, forming when molten droplets cooled rapidly in space. Similarly, igneous meteorites' mineral composition and texture, like the interlocking crystals in basaltic achondrites, reveal the conditions--such as temperature and pressure--at which these materials initially came together. In stone chondrites, primary structures manifest through chondrule accretion, while iron meteorites appear as the diffusion of Fe and Ni atoms during primary cooling and their initial crystallization. These primary structures serve as measurable variations in chemical and physical properties, acting as the original blueprint for petrologists and meteoriticists seeking to unravel their histories. The Marks of Time: Secondary Structures In contrast, secondary structures emerge after the meteorite's initial formation due to processes such as heat, pressure, impacts, or hydrous alteration on their parent bodies. These can be thought of as "scars" or recrystallization that tell the meteorite's life story, resulting from external influences like shock, impact, or solar heating effects. For instance, metamorphism-where heat and pressure recrystallize minerals-alters primary features like chondrules in some meteorites. Impact breccias, mixtures of rock fragments fused by shock from collisions in space, represent another example. In rare cases, such as carbonaceous chondrites, signs of aqueous alteration appear, including the formation of carbonates or clays through interactions with liquid water on the parent body. These secondary structures develop after cooling and highlight the dynamic changes meteorites undergo, providing a roadmap for understanding their evolution. Inclusions and Their Interpretation The study of inclusions adds further complexity to meteorite analysis, but the reveal can be thought-provoking. Think of the troilite "spiders" in Willamette! In geology, a principle suggests that fragments inside a host rock are older than the host itself, but this requires careful application in meteoritics. For example, the inclusion of schreibersite in an iron meteorite doesn't necessarily predate its surrounding minerals; instead, it forms later in the cooling process. The site "Primary and Secondary Structures - Meteorites" and resources like Meteoritestructures.org utilize high-resolution imagery and microscopy techniques to uncover these intricate details, showcasing significant inclusions and structures to supplement research and academic discussions. Such tools allow readers to engage deeply in the subject, ideally on a desktop, laptop, or tablet, for the best experience. Meteorites in Science and Culture Investigating both primary and secondary structures helps to reconstruct not only the meteorite's history, but also the broader evolution of our solar system. Many people are now interested in meteorites. They are collectibles and have become the central theme in some movies and books. This site, Meteoritestructures.org, is about the science side of meteorites, presenting some of what has been found "in" and "on" them. Fifty of some of the most researched inclusions, structures, and published terms in meteoritics are presented here. The site has put a face on them, identifying them in high-resolution images suitable for further publication to supplement research papers and academic lectures. In 1983, Robert Hutchison, the esteemed Curator of Meteorites at the Natural History Museum, London, UK, wrote a book about meteorites titled "The Search for Our Beginning." The title is profound. A systematic study of meteorites, at any level, from private collectors to professional meteoriticists, is, in many ways, a search for our beginning. You may agree when you study the images in the following 50 pages. RK All imagery was produced by New England Meteoritical Services using laboratory-prepared specimens held in the NEMS meteorite collection. The imagery is copyright protected, 2024, 2025. The high-res images of all specimens are available in digital form for scholarly publications, lecture series, and educational websites. Please contact us for the customary publishing release and limitations. |
| Contact: Staff@meteoritestructures.org |
| Listing of Structures |
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