The outline of surface chemistry on Callisto presented in the story is basically correct. A detailed outline of how complex molecules can be created is found in the papers [M.L. Delitsky and A.L. Lane, J. of Geophysical Research 102, 16385 (1997); M.L. Delitsky and A.L. Lane, J. of Geophysical Research 103, 31391 (1998)]. In these papers the authors show how complex molecules such as methanol, carbonic acid, formic acid, ketene, ethylene glycol and acetic acid can be created on Jupiter's moons. The work only used water and carbon dioxide as starting points; with NH₄-bearing clays on Callisto, much more complicated surface chemistry could arise from UV irradiation and ion implantation.