Tweet of Feb 13th from Hussein clearly seems coded. Question whether it's Alliance in control of his account (sending message to Cabal), or Hussein (sending message to Cabal). But note that the @marsrovers Twitter page still has the pinned Tweet from the same day – Feb 13th, which reads: "Rest well, rover. Your mission is complete."
Rover is an old-fashioned term for "dog". Cf. Comey's dog tweet.