No, that is not a sunspot on Mars!

No, that is not a sunspot on Mars!
Click for original image.

Cool image time! The picture to the right, cropped to post here, was taken on April 20, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). While at first glance this Martian terrain vaguely resembles the granular surface of the Sun, with the largest depression having its own faint resemblance to a sunspot, the resemblance exists only in our feverish imagination.

The depression might have been formed by an impact, though it is also possible it is a caldera, not of lava but of ice processes. The granular surface is likely resulting from the sublimation of ice, creating random holes and ridges as underground material changes from ice to gas and escapes at weak points on the surface.

My guess that we are looking at ice processes is based on the location, not far from where the first manned spacecraft will likely land.
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The icy Phlegra Mountains: Mars’ future second city

Icy glaciers in the Phlegra Mountains of Mars
Click for full image.

About a thousand miles to the west of the candidate landing site for SpaceX’s Starship spacecraft rises a massive mountain wall dubbed the Phlegra Mountains, rising as much as 11,000 feet above the adjacent lowland northern plains.

Phlegra Montes (its official name) is of special interest because of its apparent icy nature. Here practically every photograph taken by any orbiter appears to show immense glacial flows of some kind, with some glaciers coming down canyons and hollows [#1], some filling craters [#2], some forming wide aprons [#3] at the base of mountains and even at the mountains’ highest peaks [#4], and some filling the flats [#5] beyond the mountain foothills.

And then there are the images that show almost all these types of glaciers, plus others [#6]. Today’s cool image above is an example of this. In this one photo we can see filled craters, aprons below peaks, and flows moving down canyons. It is as if a thick layer of ice has partly buried everything up the highest elevations.

None of this has gone unnoticed by scientists. For the past decade they have repeatedly published papers noting these features and their icy appearance, concluding that the Phlegra Mountains are home to ample buried ice. SpaceX even had one image taken here [#3] as a candidate landing site for Starship, though this is clearly not their primary choice at this time.

The map below gives an overview of the mountains, their relationship to the Starship landing site, and the location by number of the images listed above.
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