In my review of the November image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), I am, as a cave explorer and cartographer, naturally attracted to any image with “pit” in the title. The image to the right, cropped, rotated and reduced to post here, was released with the title “Pit in Mid-Latitude Mantle”. That immediately caught my eye, and in looking at it I was at first unimpressed. The three apparent collapses are interesting in that they all have south-facing sharp cliffs, but other than that I wasn’t sure why they were of interest.
Then I took at look at this image’s location. It is somewhat far south on Mars, at latitude -60 degrees, sitting south of Hellas Basin, the deepest basin on Mars. This location is in the same general area where scientists announced in January the discovery of eight cliffs with visible exposed ice layers. The white horizontal bar below Hellas Basin on the map below and to the right shows the region where seven of those ice cliffs were located. To quote the January press release:
These eight scarps, with slopes as steep as 55 degrees, reveal new information about the internal layered structure of previously detected underground ice sheets in Mars’ middle latitudes.
The ice was likely deposited as snow long ago. The deposits are exposed in cross section as relatively pure water ice, capped by a layer one to two yards (or meters) thick of ice-cemented rock and dust. They hold clues about Mars’ climate history. They also may make frozen water more accessible than previously thought to future robotic or human exploration missions.
Researchers who located and studied the scarp sites with the High Resolution Imaging Science Experiment (HiRISE) camera on MRO reported the findings today in the journal Science. The sites are in both northern and southern hemispheres of Mars, at latitudes from about 55 to 58 degrees, equivalent on Earth to Scotland or the tip of South America. “There is shallow ground ice under roughly a third of the Martian surface, which records the recent history of Mars,” said the study’s lead author, Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Flagstaff, Arizona. “What we’ve seen here are cross-sections through the ice that give us a 3-D view with more detail than ever before.”
In an email correspondence today with Dr. Dundas, he confirmed that the image to the right was of ice cliffs not included in the January paper. The image was a follow-up of an earlier MRO image and was taken to confirm the ice cliff’s existence.
What I noticed in reviewing the January paper was that these three new ice scarps were actually outside the white bar on the map above, located at -60.7 degrees latitude, 83.5 degrees longitude.
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