This study expands upon an existing experiment to measure the seismic properties of off-Earth regolith simulants at varying atmospheric pressures. Reducing atmospheric pressure appeared to reduce the measured seismic velocity and increase the attenuation, and possible explanations for this are explored. The Australian Lunar Regolith Simulant (ALRS-1) was measured to have a P-wave velocity of 98.6 m/s using a piezoelectric transducer of with a source frequency of 54 kHz, and the Mars Mojave Simulant (MMS) dust was measured to have a P-wave velocity of 83.1 m/s, 61.3 m/s and 72.6 m/s using three different source frequencies (24 kHz, 54 kHz and 150 kHz respectively).
Determining the structure and geomechanics of planetary bodies (e.g. the Moon, Mars and asteroids) is crucial for understanding the history of rocky bodies and for planning exploration, mining, colonization, and (for small planetary bodies, i.e. asteroids and comets) deflection. For example, SPBs may react differently to deflection measures based on their structural type (Gibbings & Vasile 2011). Understanding the subsurface of off-Earth bodies will assist in understanding the presence and distribution of potentially valuable resources, and knowledge of the rock strength will dictate what mining method should be used, if feasible at all.
Seismic exploration is a geophysical method that has seen widespread use in terrestrial exploration in the last century. It is proposed that seismic sources and receivers could be emplaced on planetary bodies to determine their subsurface properties, including structure, porosity and geomechanical strength. However, to date this technique has seen relatively little use off-Earth, and little testing has been performed to determine whether the feasibility and data quality of seismic is adversely affected by various planetary environments (Pike et al 1996), for example differing gravitational strength, atmospheric thickness, electrostatics and large temperature fluctuations.
In this study we will expand upon a novel method of determining the P-wave velocity of fine grained, low compaction regolith using active source piezoelectric transducers to measure it in low atmospheric pressure (Dello-Iacovo et al 2017). This work is amongst the first of its nature.