Karel Schrijver BooksKarel Schrijver is a retired space scientist living in the Portland area. One of Ten Billion Earths, 2018, Oxford University PressPurchased after an Exoplanet lecture at OMSI on November 13, 2018p078 penultimate paragraph: Eris is a "scattered disk" object. The scattered disk reaches twice as far as the 50 AU Kuiper belt.- p115 last paragraph: Ceres may be as much as 30% water, "possibly contains a few times as much as all water on Earth combined". No Ceres mass is 9.39e20 kg, 30% of that is 2.8e20 kg . The mass of the Earth's hydrosphere is 1.4e18 metric tonnes or 1.4e21 kg. According to this 2014 Scientific American article, the mantle contains as much water (as mineral hydroxide) as the ocean. So, Ceres contains less than 10% of the water that the Earth does. Still, that is a huge amount of water, far more than the surface of Mars or the Moon, at the bottom of a 510 m/s gravity well, and may enable vast asteroid-belt settlement.