re: Origin cannot be proven yet.
"The fact that Methane escapes in the spring and summer is probably related to warming and cracking of near-surface frozen ground. The methane probably comes up from deeper underground, and may be animal, vegetable, or mineral in origin."
Either way, it would be interesting. Presently, we stipulate that Mars is presently a 'dead planet'. In other words, Mars's dynamo or core has long been cooled. So, if Mars' methane comes from underground, it would still hold some tantalizing questions especially if the methane seems to be replenishing., i.e., replenishing from season to season and on the same locations.
So far Mars does not cease to amaze.