Mmm, yes, very curious, very interesting...
I agree with the shadow. Doesn't look like a water stain...
I thought the same but the residue is well within the shaded area with no evident "hip" in the rock at that precise point to create a ridge shadow. The actual shadow termination line is located well below the residue.
Still, with this low quality artifact infested resolution. we can't be sure either way.
The most fascinating data point in this image though is found at the very top of this out cropping. When I spotted the telltale alien creation, I recognized it straight away...their artistic signature is unmistakable. However, I freely admit there will be 3 responses to seeing this: 1. Yep, I see it and get it. 2. Yep, I see it and I don't agree, 3. Nope, I don't see anything. (I say that with all respect).
For me, I can say that after four years of intense close up analysis of hundreds of MRO high resolution images, the resident artwork (presumably) is quite unique and tormentingly unbelievable - sort of "hauntingly cartoonnized caricatures" with a slight bent or propensity for ghostly human humor. See if you can spot it even with direction arrows.The best results however are in anaglyph as the raw data mast cam image has nowhere near the level of artifacts.
Last edited by M-Albion-3D; 09-20-2016 at 08:27 AM.