Skylights are recently-discovered “holes” on the surface of the Moon and Mars that may lead to planetary caves. These vast, stadium-sized openings represent an unparalleled opportunity to access subterranean spaces on other planets. This research thrust developed robotic mechanisms and operations concepts for exploration of these features. Tyrobot (“Tyrolean Robot”) was developed to map skylight walls and floors by suspending on a cable tightrope. PitCrawler is a wheeled robot which utilizes flexible chassis, extremely low center-of-gravity, and energetic maneuvering to negotiate bouldered floors and sloped descents. We demonstrated these prototypes in analog pit mines which simulated the size and shape of lunar skylights.