How is water vapour released from Ceres?

Remote observations from ground and space and in-situ exploration by the Dawn spacecraft have revealed a transient water exosphere around dwarf planet (1) Ceres, demonstrating that water ice is ubiquitous in the outer asteroid belt. However, no clear conclusion has been reached about the process that drives the release of water vapour from the surface or subsurface of Ceres. We will summarize the available evidence and estimate the contribution from various suggested processes.