Considerations for Lava Tube Exploration

Abstract:

Lava tubes are evacuated pathways within lava flows and are common volcanic features on Earth, the Moon, and Mars. Lava tube caves (i.e., preserved and accessible tube segments) provide a window into lava flow interiors that can illuminate lava flow dynamics, produce environmental niches, host subsurface water, and preserve pristine lava samples. In addition to their potential as science exploration targets of interest, for decades lava tubes have been suggested as locations to place long-term habitats for human explorers of other planets. Primarily due to the overburden of meters of rock, these void spaces can shield crews and other assets from hazards including radiation, large thermal variations, and micrometeoroid impacts. Before robotic or human explorers enter lava tubes on other planetary bodies, we need to build up some expectations for what will be found. Not all tubes will be large enough for accessibility or habitation nor will they have characteristics that permit mobility of rovers or crew. This e-lightning presentation will discuss some parameters that we can measure / explore in terrestrial lava tubes that will have direct implications for exploration wherever lava tubes are found.

Parameters discussed will include:

• Tube size (height, width, cross-sectional area)
• Tube shape (in cross-section), sinuosity, and branching
• Tube depth (i.e., overburden thickness)
• Entrance accessibility (e.g., slope, vertical drop, fraction blocked, area)
• Floor traversability (slope and roughness)
• Tube stability (ceiling fractures, pit chains)
• Environmental isolation (habitats, cold traps, perennial ice)

The presentation will give examples of lava tubes that occupy end members of the parameters and examples where tube properties change along the tube length. We will further explore how (or if) the endmember properties could be distinguished on the Moon or Mars before entering the tube.