I am posting an update of this disc-looking anomaly for the purpose of supporting Zorgon with his intent to put this on a web page, and to again include pertinent photos now not available on the July 2012 post here.
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I found this disc shaped anomaly near the Mars South Pole while researching CTX orbiter photos. This anomalous feature is so obvious to the eye to be significantly different there in the local surface area - we could say, "this anomaly sticks out like a sore thumb", as it is so different there on the Mars surface
For this update, I am posting the original CTX photo, and I am also posting the now same CTX photo with a different/changed look. I am also posting a corresponding HIRISE orbiter photo that also shows this disc-looking anomaly in similarly clear detail.
The original CTX photo:
(https://s27.postimg.org/bul27ynf7/Screen_shot_2011_08_11_at_6_39_36_PM_jpg_pst.jpg)
The now revised CTX photo: (same number as original) http://viewer.mars.asu.edu/planetview/inst/ctx/P11_005338_0878_XI_87S084W#P=P11_005338_0878_XI_87S084W&T=2&start=
(https://s23.postimg.org/zcs1vzl7f/Altered_CTX_Photo_Screen_Shot_2016_12_20_at_9_29.jpg)
HRISE photo: http://themis-data.asu.edu/planetview/inst/hirise/ESP_014436_0920_RED#P=ESP_014436_0920_RED&T=2&start=
(https://s27.postimg.org/504fa3bhf/HIRISE_Screen_Shot_2016_12_21_at_4_34_52_PM_TIFF.jpg)