Newt Gingrich says he has a “visionary” speech on space planned for Thursday. The GOP presidential candidate, a longtime advocate of establishing moon colonies, might want to prepare by reading a new paper in the journal ‘Astrobiology’ that attempts to rate nearby planets and moons in terms of habitability. The Economist’s “Daily Chart” blog helpfully graphed the results:

Earth, incidentally, gets dinged for insufficient “tidal flexing.”