Assessing Dwarf Planet Ceres’ Past and Present Habitability Potential

The dwarf planet Ceres has more water than any other body in the inner solar system after Earth (in absolute amount). Abundant ammonia and carbon species on its surface suggests it is likely an interloper from the outer solar system. Between 2015-2018, the Dawn mission performed extensive geological, compositional, and geophysical observations of Ceres on a global scale. These observations revealed a body that has been subject to pervasive aqueous alteration, with a chemically- and physically-layered interior resulting from ice-rock fractionation. Ceres surface is a globally homogeneous mixture of phyllosilicates and carbonates with a dark agent, likely consisting of iron compounds and amorphous carbon. Ceres low-density and high-strength crust suggests a rich mixture of ice, hydrates (salts and gas), silicates, and likely organics. Numerous local sites are compositionally distinct, with carbonate-rich deposits, organic-rich areas, and landmarks testifying of recent geological activity.

Dawn painted the portrait of an exceptional dwarf planet, likely a former ocean world that might still hold a relict ocean and has lost a significant amount of ice. The mission revealed the role of brines in driving long-term activity in an otherwise heat-starved object and the role of impacts in creating local liquid environments that could represent potential habitable niches.

This, combined with an apparent abundance of organics in the shallow subsurface, leads to key questions about Ceres past and present habitability potential that cannot be resolved with Dawn observations:

Did Ceres originate between the orbits of the giant planets or in the Kuiper belt? What is Ceres crustal composition and the structure of its upper crust? Has Ceres lost a significant amount of water ice? What are the characteristics of the Ceres volatile cycle, including the role of impacts and the origin and attributes of the vapor plumes? What were the environmental conditions in Ceres early ocean? Were these amenable to prebiotic chemistry? What are the origin and nature of Ceres organics? Does Ceres still contain liquid, and in which form and extent? Is cryovolcanism ongoing at Occator or Ahuna Mons? Are there regions in Ceres (e.g., source of the faculae) where chemical energy is still available?

Their resolution will require a combination of high-resolution geological and geophysical observations from orbit with in situ chemical measurements (elemental, mineralogical, isotopic) at multiple sites, possibly in combination with sample return. The proposed study will focus on a multi-element architecture (orbiter with one or multiple deployable elements) and address (1) the definition of testable hypotheses leading to quantitative measurement requirements (i.e., a science traceability matrix); (2) various payload options based on existing and emerging techniques that can address these requirements; (3) the design of in situ investigations and mobile platform and the feasibility and risk of accessing multiple sites; (4) the approach for and cost impact of returning samples to Earth; (5) the aspects and cost of planetary protection; (6) an end-to- end mission design for possible launch dates. These activities will include an assessment of technologies that can be readily leveraged from previous and ongoing projects (e.g., Dawn, Mars missions, Europa lander), and provide an assessment of technology needs in the next decade to enable future Ceres exploration.

This study will lead to a spectrum of architectures ranging from the New Frontiers to small flagship ($1.5+B) cost caps. This will allow the Decadal Survey committee to assess science return vs. cost for sensible implementations that can determine the astrobiological significance of the closest dwarf planet to Earth.