May have found the source...(s)

And you may get the prix de insight .

Took me a while to figure out where this plume (or whatever it is) was in relation to Tharsis landmarks. After much headscratching and compare/contrast exercises, it seems to be directly north of Ascraeus Mons, in the Ceraunius Fossae formation.... (of course I could be wrong, and there would be nothing wrong with that!)

http://barsoom.msss.com/moc_gallery/e01_e06/mc09.html

Guess what we find there in some abundance:

Chains of pits in graben:

http://barsoom.msss.com/moc_gallery/e01_e06/images/E05/E0503255.html

http://barsoom.msss.com/moc_gallery/e01_e06/images/E02/E0202159.html

http://barsoom.msss.com/moc_gallery/e01_e06/images/E04/E0400546.html

Now it is my understanding that these chains of pits result from the collapse of the surface into the voids (oh, all right, caves) left by the drainage of lavas and such. Such collapses might be accompanied by the venting of volatiles, mightn't they?

No way to tell from the images what the age of any of the pits is, but they look relatively recent.

As for season, what does 6/19/2001 correspond to on Mars? I just dunno!

Cheers, B R Felix