The In Situ Exploration of a Relict Ocean World: An Assessment of Potential Landing and Sampling Sites for a Future Mission to the Surface of Ceres

The Dawn orbiter's exploration of Ceres, the most water-rich body in the inner solar system after Earth, revealed the dwarf planet to be a relict ocean world of great interest to the astrobiology and ocean worlds communities. Evidence for an early global subsurface ocean is preserved in Ceres' surface minerals. While most of the subsurface ocean froze billions of years ago, its liquid (preserved in a deep brine reservoir) and solid remnants are responsible for spectacular surface features such as the faculae in the Occator crater, Ahuna Mons, and Haulani crater. Therefore, the next step in Ceres exploration is an in situ mission to the surface, with these three features being among the most scientifically compelling targets. Here we demonstrate the process of identifying potential landing/sampling sites. Using the highest resolution data obtained by Dawn (up to similar to 5 m/pixel in Occator and up to similar to 35 m/pixel elsewhere), we identify safe and scientifically compelling potential landing/sampling sites in these three regions. For future landing/sample return, higher spatial resolution data (a few decimeters per pixel to similar to 1 m/pixel) than are currently available are needed to identify hazards on the scale of a similar to 1-5 m lander. Such data could be obtained in an orbital reconnaissance phase prior to landing/sampling. Orbital reconnaissance, in combination with terrain relative navigation/hazard avoidance, and the ability to land within a <= 100 m diameter circle (>800,000 of which fit within Occator), makes it highly likely that safe and scientifically compelling landing/sampling sites could be reached by a future in situ mission.

Automated summary

The Dawn orbiter's exploration of Ceres revealed it to be a relict ocean world with evidence of an early global subsurface ocean. Features such as the faculae in the Occator crater, Ahuna Mons, and Haulani crater are believed to be remnants of this ancient ocean. Future exploration of Ceres may involve in situ missions to these scientifically compelling landing/sampling sites identified through orbital reconnaissance and terrain relative navigation/hazard avoidance.