The images here presented only show the north polar region (npr):
The top image is the one seen near from LCM=160°W,
the middle near from LCM= 210°W
and the bottom one near from LCM=305°W.
The images of the npr show that the details of the npc and its
surroundings are not so different from those shown in the images obtained in
the 1970s by Mariner 9 and/or Viking Orbitors. It is very impressive to be
able to find a white spot which may be identified with the Korolev crater
(196°W, 73°N) shown already in the Mariner Map in 1972 cited in No177
p1872. Is it possible to consider that the snow on the crater has remained
iced more than twenty years?
Other details around Rima Borealis look also the same. Thus we may be allowed to think that the npc remnant including the rifts near summer has repeatedly shown the same aspect for a long time.
(Mk & Mn)