by Jim Nintzel
It's been a while since we shared new photos of Mars taken by the UA Lunar and Planetary Lab's HiRISE camera aboard the Mars Reconnaissance Orbiter.
The upper photo is an oblique view of Victoria Crater. Dr. Alfred McEwen of the LPL tells us:
Victoria Crater was explored by Opportunity rover for more than a Mars year; HiRISE images have supported surface exploration and contributed to joint scientific studies.
HiRISE stereo data were used to measure slopes and help select safe paths for the intrepid rover. The most interesting exposures of geologic strata are in the steep walls of the crater, difficult to image from the overhead perspective of orbiting spacecraft like MRO. However, MRO can point to the sides, and did so in this case to get a better view of layers in the west-facing and sunlit slopes of the crater.
Especially prominent is a bright band near the top of the crater wall, interpreted by some MER scientists as
having formed by diagenesis (chemical and physical changes in sediments after deposition). This bright band separates the bedrock from the impact ejecta deposits of Victoria Crater.
The subimage image has been rotated so that we are looking east, with MRO pointed 22 degrees east of straight down, so it is comparable to a view from an airplane window. Colors have been enhanced to show subtle differences.
Some of the rover tracks are still visible to the north of the crater (left side of the subimage).
The lower photo is an interesting crater in Meridiani Planum. LPL description:
In addition to the interesting light-colored material near the top rim, this formation almost resembles a crater within a crater.
Could material have filled in the original crater only to be blown out a second time? Or could the material in the crater have collapsed, giving the appearance of a second impact?
The full observation image still shows the ejecta pattern from the original impact, although it's clear the blown-out material has eroded over time.