The Man Who Loved Mars. Lin Carter

      “But the main problem with Phobos is not that it is much too dim and dark to show up very well, but it whizzes by so rapidly that you never know just where in the sky to look for it at any given time. You have to search the sky from horizon to horizon, slowly and carefully, and even then, under the best of conditions you’d have to be mighty lucky to—”

      I broke off as moss rustled and squeaked under heavy boots behind me.

      “Your first lesson in Marsology, my dear?” Dr. Keresny broke in amiably. “Forgive me for interrupting, but the skimmer is all packed. Cn. Tengren, we are ready when you are.”