Could liquid water have such a thermal behaviour?
The HIRISE image you can find between -6,-5N and 240, 242 E ("
Candidate Cavern Entrance Northeast of Arsia Mons "), perhaps could be "just" a small water lake. Or not?
There's plenty of ice in Mars underground; that one is a volcanic (=maybe hot) region; couldn't some ice be melted down and create a lake? Water would evaporate, but it would be "replaced" by other melting ice, so keeping the lake alive.
Are you able to find day and night IR images at higher res for the "candidate cavern"? I'm trying with no success.
