Free-Floating Planets, or as they are more commonly known, Rogue Planets, wander interstellar space completely alone. Saying there might be a lot of them is a bit of an understatement. Recent estimates put the number of Rogue Planets at something equivalent to the number of stars in our galaxy. Some of them, undoubtedly, are accompanied by moons - and some of those might even be the size of Earth. A new paper, accepted for publication into the Monthly Notices of the Royal Astronomical Society, and also available in pre-print on arXiv, by David Dahlbdding of the Ludwig Maximilian University of Munich and his co-authors, describes how some of those rogue exo-moons might even have liquid water on their surfaces.