THE TREASURE OF PLANETARY CAVES

Planetary caves on the Moon and Mars have long been a subject of fascination and the setting of fictional adventures. Today, more than a thousand candidate cave entrances on the Moon and Mars have been identified, using satellite imagery, as sky lights, collapse pits, and cave mouths, all apparently formed from basaltic flows. Ground penetrating radar, also from orbit, has been used to infer the size of a lunar cavity, though in general we will not know the extent of corresponding subsurface voids until they are characterized by a robotic or human visitor.

Volcanic caves provide direct entry into the shallow underground, where signs of past or extant life could be protected from harsh conditions on the surface. Cold sinks in caves could be a repository for ice and pristine organic compounds therein. On Earth, lava cave interiors are lined with mineral coatings and biofilms, usually associated with an aqueous history. Other mineralized evidence of life in lava caves persists in the form of speleothems, dominated compositionally by cryptocrystalline silica and lesser amounts of embedded carbonate. These minerals could be preserved over geological timescales and offer a record of ancient climate or life.

The first explorers to reach a planetary cave will likely be robots. Current technological and mechanical limitations associated with cave ingress and navigation are being challenged in terrestrial environments by new advances in robotic mobility and autonomy.

In celebration of the International Year of Caves and Karst, I will review our current knowledge of planetary caves, focusing on their putative occurrence on the Moon and Mars and the developing technologies bringing the goal of their access closer to possibility. This presentation will address current and on-going technology developments that could advance planetary cave identification, access, communications relays, and autonomous exploration and sensing for application to future sites on Mars and beyond. I will also cite current ongoing human and robotic exercises in lava caves on Earth that target operational activities that may one day be relevant to a planetary cave mission.