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Did you know there are caves on Mars? Lava tubes more precisely. When I was at NASA Ames Research Center, I worked on a project called Assessing Cave Capabilities and Evaluating Specific Solutions (ACCESS) Mars, to determine if underground habitation is more feasible for humans than surface habitation. ACCESS Mars explores the future of robotic and human Martian exploration via subsurface habitation.

The understanding of the Martian environment has changed over time to a planet with ice, methane, and formaldehyde that represent a warmer, wetter, and more active past. And with this new understanding of the Martian environment come changes in the vision of future Martian Design Reference Missions. This includes numerous challenges of a human mission to Mars such as high levels of radiation, climate, limited launch windows, and length of stay on the planet. However, recently discovered lava tubes on Mars offer possible solutions to improve the feasibility of a human mission. Keep in mind that there are other challenges to subsurface habitation including legal and ethical issues.

One possible location for consideration as an initial settlement on Mars is its lava tubes. Recent Mars Reconnaissance Orbiter camera data have proven the existence of lava tubes on Mars (Boston, 2008; Cushing et al., 2007) and recently posted in November on Space.com.

Literature suggests that Martian caves have a low radiation environment, which would be critical for allowing an extended duration mission. The ACCESS Mars Team concluded that “using lava tubes as human habitats is not merely a viable habitat solution for a Mars expedition, but also potentially more beneficial than proposed surface solutions.”

A lava tube is a cave created when low viscosity basaltic lava flows from a non-explosive volcano (Greeley, 1975). The lava tubes can form through: cooling and solidification, lava splatter building up in a turbulent flow, or fluid lava streams flowing inside a more viscous stream, all of which result in an empty tube coated with lava on the floor, walls and ceiling, with a smooth surface (Greeley, 1971).

But there are some very definitive challenges with an underground settlement. What type of cave or where and how to find the caves? How to establish a base under the surface and how will humans react to living underground for prolonged periods of time?

The simplicity of lava tubes is advantageous to mission planning and mission development and makes subsurface habitat planning easier. Physical and thermal properties of lava tubes also show benefits for cave habitation; however, their feasibility largely depends on their ability for hazard mitigation. While many risks to crew are reduced in a cave habitat, other risks may be introduced. Conceivable trade-offs include radiation, meteorites, dust storms, cave instability, risk of injury during Extravehicular Activities (EVA), communication, and electric discharging.

The full report can be found here:
http://isulibrary.isunet.edu/opac/index.php?lvl=notice_display&id=3630