‘Icy’ Ceres because of water vapour?

icy ceres water vapour rocky rockDoes the dwarf planet Ceres have an icy surface and mantel due only to the water vapour discovered coming from its surface?

Or is it a combination of the water vapour and planetary science theory about large asteroids or objects in the asteroid belt?

Icy Ceres

"This is the first time water vapor has been unequivocally detected on Ceres or any other object in the asteroid belt and provides proof that Ceres has an icy surface and an atmosphere," said Michael Küppers of the European Space Agency, and the lead author of the paper.
Water vapor on mysterious dwarf planet intrigues scientists

Before this was it just a very large rocky asteroid before it was re classified as a dwarf planet?

Icy Ceres or rocky asteroid Ceres

Will Ceres have a rocky surface with no or little sign of ice? So that the ice that sublimates (turns directly from ice to gas in freezing cold space) has to be under the surface?

Could the water source of Ceres be an electrical phenomenon, similar to other comets like comet 67P and perhaps on the moon due to a form of electron spluttering?