Nothing, really. It's just a stock phrase. Japan has a few of them. It CAN be translated, literally, as "it is so".
Nano (なの) is a "sentence-ender", something that people use to give their words more life when talking. Generally, nano is used by females to beautify their sentences.
Some ships that use nano include Haruna and Iku (I-19).
Desu (です) is a more formal sentence-ender that can be used by anyone. Typically, statements will end with desu, although it is usually not needed and people will use other sentence-enders to fit the situation, such as a verb-masu.
hi there, where are we going to go nano desu