Meteorites demystified: A beginner’s guide (Part 2)

Helen Gould (UK) Chemistry is the key to identifying the source of a meteorite. The commonest rock in the Solar System – and on Earth – is basalt. Erupted at mid-ocean ridges and many hotspot volcanoes, it also floors the oceans. However, each of these situations can be identified as geochemically different from one another. Some meteorites have geochemical signatures associated with individual asteroids, being either enriched or poor in specific minerals. The ratios of their minerals are plotted against one another, then the shape and co-ordinates of the plots are cross-referenced to a database. This process has allowed distinct groups of meteorites with similar geochemistry to be identified, suggesting that the meteorites in each cluster plotted came from the same source. There are five sub-groups of achondrites of various chemical composition, including eucrites, diogenites, SNC, lunar achondrites and ureilites. The name means they don’t contain chondrules. Most are of igneous origin, but lunar achondrites resemble fragmental sedimentary rocks. The only “weathering” on the Moon comes from impacting meteorites, but this breaks up rocks and reforms them into breccias – jumbles of jagged fragments fused together. Eucrites Eucrites are basaltic meteorites containing low-calcium proxenite and plagioclase feldspar with metallic iron, troilite (iron sulphide) and silicates. They probably all crystallised at or just below the surface of their source bodies. Fig. x. Eucrite. Diogenites Diogenites consist of calciumpoor pyroxenite, which is an igneous rock resembling the ocean crust. Fig. x.. Diogenite. SNC SNC meteorites have been identified as coming from Mars. … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.
%d bloggers like this: