  Detailed surface images of the Moon and Mars reveal hundreds of cave-like
openings. These cave-like openings are theorized to be remnants of lava-tubes
and their interior maybe in pristine conditions. These locations may have well
preserved geological records of the Moon and Mars, including evidence of past
water flow and habitability. Exploration of these caves using wheeled rovers
remains a daunting challenge. These caves are likely to have entrances with
caved-in ceilings much like the lava-tubes of Arizona and New Mexico. Thus, the
entrances are nearly impossible to traverse even for experienced human hikers.
Our approach is to utilize the SphereX robot, a 3 kg, 30 cm diameter robot with
computer hardware and sensors of a smartphone attached to rocket thrusters.
Each SphereX robot can hop, roll or fly short distances in low gravity, airless
or low-pressure environments. Several SphereX robots maybe deployed to minimize
single-point failure and exploit cooperative behaviors to traverse the cave.
There are some important challenges for navigation and path planning in these
cave environments. Localization systems such as GPS are not available nor are
they easy to install due to the signal blockage from the rocks. These caves are
too dark and too large for conventional sensor such as cameras and miniature
laser sensors to perform detailed mapping and navigation. In this paper, we
identify new techniques to map these caves by performing localized, cooperative
mapping and navigation.
