A simple model is presented for describing gross aspects of lunar meteorite impact, including the gas cloud that may accompany some events. Parameters include meteorite composition (iron or stone), impact speed (3–70 km/sec), and meteorite radius (10−3–10 km). One‐dimensional shock theory, experimental high‐pressure data, and an equation of state from Zel'dovich, are used to find entropy changes in a basalt target and in a spherical meteorite. Decompression leaves irreversible heat and, above a threshold impact velocity of 12–16 km/sec, causes vaporization. At incident meteorite speeds of ≥20 km/sec, the evolved gas is found in turbulent flow of high dynamic pressure to a distance of >1000 meteorite radii. This fact verifies suggestions by H. Larson, W. Hartmann, and F. Yale that such transient winds would be capable of erosive scouring and could have produced surface patterns like some found near the Eastern Sea or Aristarchus. One specific example is that of an iron meteorite with a radius of 1 km hitting at 20 km/sec, which could have produced a crater like Clavius. The transient wind, turbulent out to 11 crater radii, could easily have lofted 1‐ton (907 kg) boulders originally located as far away as 2 crater radii from the impact center.
Many instructors use conceptual analogies between water pipes and electrical circuits, but the isomorphism of related transport equations is not as commonly appreciated. The Laws of Fourier, Ohm, and Poiseuille may all be cast into nearly identical forms for flows of heat, electric charges, and viscous fluids, respectively. Examining such formal similarities may enhance student understanding.
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