Click for full image.
Cool image time! The photo to the right, cropped and reduced to post here, was taken on July 24, 2021 by the high resolution camera of Mars Reconnaissance Orbiter (MRO) and shows one small portion of the edge of Mars’ north pole ice cap.
The many layers in that ice cap are clearly evident, with some darker because they were probably laid down at a time when the Martian atmosphere was more filled with volcanic ash. According to the presently accepted theory, the layers show the cyclical climate patterns of Mars, caused by the large shifts in its obliquity, or the tilt of the planet along its rotational axis, ranging from 11 to 60 degrees. Presently Mars is tilted 25 degrees, similar to Earth’s 23 degrees. The two extremes cause the planet’s water ice to shift back and forth from the mid-latitudes to the poles, causing the layers.
The height of this layered cliff face is probably about 1,500 feet, though that is a very rough estimate. Notice also that this image shows an ice canyon running from the left to the right and flowing into a much larger ice canyon to the right. The top cliff is probably about a third the height of the bottom cliff.
The overview map below shows gives the context, not only in place but also in time.
The red box marks the location of this image. The white boxes mark locations that MRO scientists are monitoring for the tens of thousands of avalanches that occur on the ice cap’s edge each Martian spring.
Today’s image covers terrain adjacent to one of the earliest MRO’s images that captured an avalanche in process. The labeled numbers indicate avalanche images previously featured on this site, in a September 2019 post describing Mars’ annual avalanche season.
What is interesting about this image is the left-right ice canyon. Not only is it smooth as … ice, the layers on its opposite canyon walls do not seem to match, something you would expect them to do. Why are there dark layers on the bottom wall, but not on the top wall? Is this an artifact of lighting, or is it showing us a puzzle that is real?
There are no answers to these questions at this time. But it surely is fun discovering the questions.
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