Rock-mass strength of lunar basaltic units

Determine the rock-mass strength of lunar basaltic units hosting skylights and lava tubes by constraining their fracture-network properties and geotechnical parameters.

Background

Existing lava-tube stability models commonly parameterize lunar rock-mass properties using the Geological Strength Index and values derived from terrestrial analogues. Direct observations of fracture networks in lunar basalts are limited, making the strength of the rock masses that host skylights uncertain. This uncertainty affects predictions of lava-tube and pit stability.

References

However, there have been limited observations of the fracture networks present in lunar basalts, and there is thus a critical unknown related to rock mass strength of these units.

— Lava Tube Exploration with LunarLeaper  (2609.11453 - Mittelholz et al., 10 Sep 2026) in Section 3, subsection “Stability of Lava Tubes and Pits”

Furthermore, it is known from terrestrial analogues \citep{okubo_pit_1998,roche_sub-surface_2001,zhao_failure_2022} that stoping, a discontinuum failure mode that can occur at stress levels below overall continuum failure, is a primary formation mechanism of pits in lava tubes. Although this has been suggested in previous studies \citep[e.g.][]{robinson_confirmation_2012,wagner_lunar_2022}, it has yet to be quantified in numerical models, likely due to a lack of field data regarding fracture networks within the rock masses that host skylights.

— Lava Tube Exploration with LunarLeaper  (2609.11453 - Mittelholz et al., 10 Sep 2026) in Section 3, subsection “Stability of Lava Tubes and Pits”