At only an increase of about 8 times in volume, the actual sublimation should be quite gentle, fred.
I was convinced we could view the processes as state changes at one time, but have serious doubts about the simple explanations myself now.
I prefer to make slow additions in information as confirmed, point to point, but these are a relatively unexplained set of conditions and items of colorful and localized conduct, giving little evidence of darkening due to a simple state change.
In the first MOC gallery image, the dark spots are most all mounds, not depressions. They have been irradiated and blown by swinging wind temps. all year(2 years), and now the action is on the near and far sides of mounds. There is also a ring of darkness around many of these mounds.
The mounds are a result of either knobby residual removal along the left to right channel, or a upwelling or pingo type ascent in elevation. The MOC images carry too little detail to make good judgements on many items. I would always refer to HiRISE imaging now, but that is a new source of information this new century.
I hope for more detailing of Mars with another satellite, but we have seen the social problems become the dominating political decision wielding forces lately.
There is a shaded characteristic to the left side of most all the dark spots. The sunlight would cast a shadow on that side. The wind is a follow along in direction in the same orientation, so, the dark shadows are from either the wind, or both wind and sunlight casting of shadow. There are breaks in the dark spots at sharp divisions where fault type lines interrupt the surface aged ripple patterns on the lower elevation and more textural 'flats'.
These items are as prolific in the lowest and denser levels as the smoother, more recent and looser slopes. The dark spots are larger generally in the intermediary slope runs which are exposures of layer edges. There are no substantial dark linear formation following layers viewable.
I made these observation as the very contrasty scene of bright and dark features is not informational when viewed in the image as it is issued. We see gross variation, not information on activity and surface textures.
What is not seen in part is the stable ripples across the dark areas. The alterations in these images are different from the polar dunes images of the HiRISE JP2's. The size scale prevents careful assessment of any but the largest features, in meters range.
The higher elevation on the far right has few large developed dark spots. Those spots that are viewable are small, and reasonably equally distributed by positions. The upper elevation shows a population of small dark spots with large bright extended domains.
fred is correct in that the scale is wrong for viewing items of life. Only a population would be viewed well.
Are the patterns showing what has been claimed as an 'upward migration/movement of dust'?
Are any fans, or Araneiform items viewed here?