the features has been removed. However, this is possibly not conclusive as creation
of the structures may have been part of the surface change process. Furthermore,
because of surface dust transport, we have no way of knowing if the material
removed had been only recently emplaced. Consequently, the formation process
and its timing have not been established.
2.10.13 Surface Dust Transport
One of the most remarkable observations on 67P was the evidence of what appear to
be dune ripples (Fig. 2.95). This is remarkable because, prior to these observations,
the gas velocity vector was widely assumed to be primarily radial whereas a strong
Fig. 2.93 Image of the Bes region of 67P showing an irregular depression (marked E) between two
cliffs (marked A and B). This suggests that the irregular shape of depressions produced by activity is
common. Smooth material at the base of cliff B is marked (C) and talus at the base of cliff A is also
marked (D). (Image number: N20160130T180323711ID10F22)
2.10 Surface Appearance and Cometary “Geology”
161
of the structures may have been part of the surface change process. Furthermore,
because of surface dust transport, we have no way of knowing if the material
removed had been only recently emplaced. Consequently, the formation process
and its timing have not been established.
2.10.13 Surface Dust Transport
One of the most remarkable observations on 67P was the evidence of what appear to
be dune ripples (Fig. 2.95). This is remarkable because, prior to these observations,
the gas velocity vector was widely assumed to be primarily radial whereas a strong
Fig. 2.93 Image of the Bes region of 67P showing an irregular depression (marked E) between two
cliffs (marked A and B). This suggests that the irregular shape of depressions produced by activity is
common. Smooth material at the base of cliff B is marked (C) and talus at the base of cliff A is also
marked (D). (Image number: N20160130T180323711ID10F22)
2.10 Surface Appearance and Cometary “Geology”
161