Ah, I see what you are saying. They were talking about the May 1997 event right above that photo, but it is actually just another one of the 2012 event. My mistake.
No prob’. It’s interesting that the science-critter gets quoted in some sources that these plumes shouldn’t be seen at such high altitudes, that it would mean the Earthlings’ understanding of the atmosphere of Mars is incorrect (due to the low density). Obviously it *has* to be either from an impact, or from a volcano, but again, the latter would mean current volcanic activity, and the most recent known was about 2 million years ago. :’)