This image was taken by NASA’s Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) on 2007-11-25T12:48:43.748.
NASA describes this photograph as “Protonilus Mensae.”
I discovered what might be a massive cave entrance on the side of a hill on the Martian surface. It does not look like any of the craters in the area and is definitely out of place. The craters have geological formations inside them which this anomaly does not exhibit.
Looking inside the entrance you can see the tell-tale signs that there must have been water that dammed up there and evaporated some time ago.
There is also a structure which forms an arch to the right. The shadow inside the entrance extends from the far left to the far right and is visible in the main entrance as well as in the smaller archway entrance.
I enhanced the photograph by adjusting the contrast and brightness and discovered what looks like mechanical parts inside and outside the cave entrance.
The parts seem to include pipes bent at 90 degrees and large loops, a triangular grid and other misc. stuff I cannot classify.
Near the cave I also found a crater containing other mechanical parts and after adjusting the contrast and brightness of this area I discovered two square plates and more pipes.
The larger square plate seems to have a long pipe joined to its top left corner and there are two parallel pipes at the bottom of the smaller square plate.
Original NASA source: http://viewer.mars.asu.edu/planetview/inst/ctx/P13_006238_2219_XN_41N303W
I used NASA’s image viewer to the left of the NASA web page to view this anomaly (the anomaly is located at the bottom of the photograph).
Is this indeed a cave entrance or the side of the hill that sunk beneath the surface?
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