  We report on the first major temporal morphological changes observed on the
surface of the nucleus of comet 67P/Churyumov-Gerasimenko, in the smooth
terrains of the Imhotep region. We use images of the OSIRIS cameras onboard
Rosetta to follow the temporal changes from 24 May 2015 to 11 July 2015. The
morphological changes observed on the surface are visible in the form of
roundish features, which are growing in size from a given location in a
preferential direction, at a rate of 5.6 - 8.1$\times$10$^{-5}$ m s$^{-1}$
during the observational period. The location where changes started and the
contours of the expanding features are bluer than the surroundings, suggesting
the presence of ices (H$_2$O and/or CO$_2$) exposed on the surface. However,
sublimation of ices alone is not sufficient to explain the observed expanding
features. No significant variations in the dust activity pattern are observed
during the period of changes.
