[baggy_trough]

If that's the case why would it be an ocean at all, rather than a block of ice?

[ojnabieoot]

The article said it was a brine ocean, so salinity or some other solute - even at Earth gravity and air pressure, highly saline water can have a freezing point as low as -20C.

[baggy_trough]

The maximum surface temperature on Ceres is -118C. How would you get to -20C without geological heating?

[api]

Pressure? Water unlike most materials expands when it freezes.

[darkerside]

When you apply pressure to ice, does it melt or freeze?

Google says, https://van.physics.illinois.edu/qa/listing.php?id=1593