The moving glaciers are mostly thought to be in the dark troughs on
the edge of the dry ice topping the perennial cap, flowing down to
pond on the water ice below.

The uncertainty of science: According to a newly published paper, scientists have concluded that some of the dry ice glaciers at the Martian south pole ice cap are still active and moving, flowing into basins which allow them to survive longer during warm periods.

From the paper’s abstract:

Carbon dioxide (CO2) ice is found in a stack of deposits at Mars’ south pole. These deposits are situated in basins, where they reach more than 1 km thick. Previous work suggested that the CO2 ice should be deposited when the axial tilt of the planet was lower, making the poles colder than they are now; however, the thickness and distribution of this ice should be much thinner than observed if only atmospheric effects are working on the ice. Therefore, the CO2 ice deposit distribution cannot be explained by atmospheric deposition alone. In this paper, we use glacial modeling and feature analysis to demonstrate that glacial flow better explains the distribution of ice in its present state. In addition, we show that the slopes on the south polar cap act to focus glacial flow into the basins, where it can survive warm periods by sublimating only the uppermost sections when the tilt of the planet is larger than present day.

The scientists estimate that the motion of these glaciers began approximately 600,000 years ago. According to Isaac Smith of the Planetary Science Institute in Arizona, the paper’s lead author:

“The longest glacier is about 200 kilometers long and about 40 kilometers across. These are big! That activity is ongoing, but flow rates probably peaked about 400,000 years ago when deposition was greatest. We’re in a slow period because the [dry] ice is decreasing in mass, and that slows down glaciers.”

This conclusion however is not confirmed, since to date no high resolution image of the glaciers has actually seen any change. From the paper:

Our search for surface translation over the relatively short baseline of Mars Reconnaissance Orbiter’s [MRO] time in orbit (∼15 years) has not detected any movement.

MRO has the resolution to see this motion, but the rate of movement, likely much less than 8 inches per year, is probably why no changes have yet been detected. Lacking visual proof, the scientists resorted to computer modeling, updating already existing models to better match the data, and consistently found that these glaciers should be moving, based on the known conditions.

Because the conclusion is not confirmed by any observational proof, however, it must be viewed with skepticism. Still, the conclusion is not unreasonable based on the known facts, and given time and now knowing exactly where to look, orbital images are likely to eventually confirm it.

If so, I think (but am unsure) that these glaciers might be the first glaciers of any kind found to be still active on Mars. All the water ice glaciers so far detected appear to be inactive at this time, neither growing nor shrinking.