Ceres: Astrobiological Target and Possible Ocean World

Abstract

Ceres, the most water-rich body in the inner solar system after Earth, has recently been recognized to have astrobiological importance. Chemical and physical measurements obtained by the Dawn mission enabled the quantification of key parameters, which helped to constrain the habitability of the inner solar system's only dwarf planet. The surface chemistry and internal structure of Ceres testify to a protracted history of reactions between liquid water, rock, and likely organic compounds. We review the clues on chemical composition, temperature, and prospects for long-term occurrence of liquid and chemical gradients. Comparisons with giant planet satellites indicate similarities both from a chemical evolution standpoint and in the physical mechanisms driving Ceres' internal evolution.

Ceres’ partial differentiation: undifferentiated crust mixing with a water-rich mantle

“…Paths 1.2 and 3.2 lead to bodies that have no rock material remaining at the surface. This contradicts Dawn's observations, unless there was a larger proto-Ceres that was stripped of the H 2 O layer and left its rocky core which represents the dwarf planet presently observed behind (Castillo-Rogez et al 2020). In any of these scenarios, except in the one where the crust never subducts, the porous thermal shield is destroyed.…”

“…The current understanding of Ceres' interior appears to converge on a brine layer at depth (Nathues et al 2017;Castillo-Rogez et al 2020;Quick et al 2019). Assuming a structure with a volatile-dominated crust and rocky mantle with remnant brines, Castillo-Rogez et al (2020) showed that Ceres should preserve a warm crust with a temperature of >220 K at the base until present if the crust is rich in clathrate hydrates, allowing for a brine layer. The structure inferred is similar to that produced in our calculations, but the density of the brine layer is higher than in the upper crust, while in our models the situation is opposite.…”

“…However, since Ceres shows clear signatures of pervasive hydrothermal activity and mobility of liquids (the mountain Ahuna Mons that was proposed to have formed as a cryovolcanic dome), both altered rock and organic-rich areas are probably the products of internal processes (De Sanctis et al 2017). Detection of surface water ice deposits (Platz et al 2016;Prettyman et al 2017;Combe et al 2019) and the potential presence of ice in Ceres' subsurface (Bland et al 2016;Ermakov et al 2017) suggest geological similarities to differentiated icy bodies (Castillo-Rogez et al 2020), as predicted by pre-Dawn models (McCord & Sotin 2005;Castillo-Rogez & McCord 2010).…”

Transformative Planetary Science with the US ELT Program

“…Furthermore, ELTs could monitor ongoing volcanic activity on Io, which supplies material to the plasma torus, subsequently modifying and enriching the surface chemistries of the icy Galilean moons Europa, Ganymede, and Callisto. Additionally, long-term monitoring of the dwarf planet Ceres, another possible ocean world that exhibits evidence for recent endogenic activity, could be conducted by ELTs to monitor changes in its surface composition (Castillo-Rogez et al, 2020).…”

What Is Life—and When Do We Search for It on Other Worlds

“…Although Venus is not a promising target by the criteria established above, it comes close. Other possible targets suggested for a life search include the clouds of Jupiter (Sagan and Salpeter, 1976), Ceres (Castillo-Rogez et al, 2020), Vesta (Houtkooper, 2011), Triton, Pluto, and even the Moon (Schulze-Makuch and Crawford, 2018). None meet the five requirements listed.…”