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Cool image time! The photo to the right, cropped and annotated to post here, was taken on September 1, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I have annotated it to note the two apparent skylights that appear aligned along a north-south depression.

The grade is downhill to the north. If you look at the full image you will see that this north-south depression extends for a considerable distance beyond the edges of the cropped image above, with that depression appearing to dissipate to the north into a series of parallel very shallow depressions, almost like the lava had flowed out of the tube and formed branching surface rivulets heading south.

The overview map shows that this tube is on the northern flanks of the volcano Arsia Mons.

The white box notes the location of these two skylights and hypothesized lava tube. The black boxes note the location of every single pit or lava tube in this region that I have previously featured as a cool image on Behind the Black. (For a listing of most of these posts go here.) These pits however form only a partial selection of the numerous such pits scientists have identified surrounding Arsia Mons.

Why there are white streaks to north edge of both pits is unknown. While it could be dust deposited by the prevailing winds, that theory doesn’t fit with the white cliff to the north. I also wonder if the winds cutting across the top of these holes could function much like a flutist blowing across his flute’s mouthpiece to produce sound. At these holes a similar wind might cause material to be pulled up out of the holes.

All guesses. We don’t even know if the skylights are connected by a lava tube underground. The depression might simply be signaling the long ago filling of that void.