All of the planets are too close to their star to be considered within the habitable zone. Although Kepler-138c and d have the same size, their masses and densities vary greatly. Of these two, the inner planet is consistent with a rocky super-Earth, whereas the outer planet's low density implies it may have a substantial proportion of water ice or a significant gas envelope, resembling a miniaturized gas giant (a Gas dwarf). The striking differences between these two planets have been hypothesized to be due photoevaporation. The KOI and Kepler letters for these planets don't match. KOI-314b and KOI-314c were confirmed by Kipping et al., but the Kepler team assigned the letters in a different order in their validation paper.