Glass production differences for equal-diameter impact craters

A thermodynamic model of meteorite impact is applied to determine if craters of equal diameter were necessarily created by events of similar thermal regimes. The particular case considered is that of a spherical basalt meteorite hitting a basalt target, and only two parameters are varied: impact velocity and meteorite radius. It is found that, in producing craters of equal diameter (20 cm), a small fast meteorite produces less melted and vaporized material, or tends to yield less glass, than does a large slow meteorite. Above 10 km s^–1 the amount of melted material is a monotonically decreasing function of impact velocity; above 20 km s^–1 the amount of vaporized material is a monotonically decreasing function of impact velocity. At 70 km s^–1 only 23% as much melt and vapor is produced as at 10 km s^–1, for events yielding equal crater diameters of 20 cm. According to the model used, this effect can be explained by observing that a meteorite with a small contact surface will deposit more heat and will produce a hotter but smaller amount of liquid than will a larger slower meteorite. Implications include, in principle, the possibility of estimating impact velocities by means of ejecta sample analysis.