The Variation of Sound Velocity with Stress in Sand

Apollo 12 lunar module impact: laboratory simulation and possible downrange ballistic effects

Plastic pellets were fired into sand targets at a launch angle of 4 degrees and a velocity of 1.68 kilometers per second, the conditions of the Apollo 12 lunar module impact. Shallow elliptical or doublet craters were formed, similar to certain lunar craters. Analysis of the ejecta suggests (i) that lunar module debris skipped and, with some crater ejecta, reimpacted far downrange, but (ii) this ballistic rain does not account for the anomalous seismic signal.

Compressional and Surface Waves in Sand: Used by Desert Scorpions to Locate Prey

Loose sand conducts compressional and surface (Rayleigh) waves at relatively low velocities (95 to 120 meters per second and 40 to 50 meters per second, respectively) compared to other natural substrates. For frequencies between 1 and 5 kilohertz, the specific attenuation factor, Q, for sand is 18. Compound slit sensilla on basitarsal leg segments of sand-dwelling scorpions respond to surface waves generated by movements of insects as far as 50 centimeters away, and tarsal sensory hairs respond to higher-frequency (mostly compressional-wave) components of the signal.