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Table 2 Reference model properties of the surface regolith of Phobos

From: Surface environment of Phobos and Phobos simulant UTPS

  Estimated range Likely values
Particle size 30 µm–10 cm Model 1: very fine (< 300 µm)
Model 2 (nominal): 100 µm-5 mm
Model 3: > 1 mm
Particle size distribution Power index 0.0–4.0 Power index ~ 3.0
Particle shape Round to very angular Subangular to angular
Internal friction angle of the particles < 10 to > 55 degrees 30–50 degrees
Cohesion of particles 0–2000 N/m2 50-700 N/m2
Compressional strength of particles 0.5–70 MPa Model a: 1–10 MPa
Model b: 30–50 MPa
Macroscopic porosity < 10–70% 40–70%
Surface mobile particle-layer thickness < 1 to > 100 m 5 m (can continue much deeper, but deeper parts are considered as mechanically stable)