The presence of the Tharsis Ridge clearly indicates massive pressures have existed in the region before, and it's the height of concete to state it cannot exist today. There are volcanoes here on Earth that have defied us over recent decades, where we thought they were dead, only to discover they were not (still waiting for Vesuvius to awaken the folks at Napoli). But the Tharsis has been inactive for quite a long period...

The odds that the camera was in position to snap a shot of collapsing rill is unheard of -- but certainly not an impossibility...

Escaping volitiles calls back to the Tharsis as a still-active site, with subterrainian (is there a Mars equivelant for this term?) volcanic activity, heating regions of permafrost and forcing emissions...

The season reference was merely toward temperature changes that would alter the state of moisture collected and frozen upon the internal walls of surface rills. Seeing as the site is very nearly on the equator, such changes would likely be negligeable.

Dan