L4Sahara Desert

To enable scientists to refer to the unique attributes of a given meteorite, there must be a nomenclature system, and so a committee of scientists name meteorites after the location to which they’ve been “delivered,” (e.g., a city, village, mountain, river, county, etc.). In a desert, where there are few distinguishing geological features, meteorites are named after a grid encompassing a restricted area and are assigned sequential numbers. NWA 10195 was found in 2013; it is the 10,195th meteorite to be catalogued following its recovery in the Northwest African grid of the Sahara Desert. The L4 classification indicates the meteorite has moderate amounts of free iron and experienced moderate metamorphism on its parent asteroid prior to launch. What most sets this meteorite apart is the characteristic of orientation. Oriented meteorites are rare and occur only when the mass of a meteorite is distributed in such a way that it maintains the same axis of orientation throughout its descent in the atmosphere. Unlike 99.9% of all meteorites, oriented meteorites don’t invert or tumble when frictional heating commences high in the atmosphere. As a result, oriented meteorites look different and their direction of flight is readily discerned. The parabola seen here is the angle at which heat is most efficiently deflected away from a falling body and inspired the heat shield design of Mercury, Gemini and Apollo capsules. The long grooves in the specimen are regmaglypts or thumbprints, a result of material streaming off the meteorite’s molten surface. Most meteorites this size are barely warm to the touch when they reach the ground. There are three main reasons for this: much like fried ice cream, the freezing-cold core of the rock tends to diminish the superheating experienced at the rock’s surface; the molten surface continually ablates away during atmospheric passage, allowing little time for heat to be conducted into the rock’s interior; and after a falling object reaches terminal velocity, it experiences a nice breeze.