Siding Spring update

At http://phys.org/print336388496.html … the approach of comet Siding Spring to the planet Mars a few weeks ago has now been updated by including images and data from the Indian space mission to Mars. A streak appears to radiate out of the comet's nucleus and it is this ejection of dust and gas that might have caused the meteor storm – but again, it may have nothing to do with dust or gas. At the same time, it is being suggested by NASA that this was a one in 8 million years event – quite how they arrive at that estimate is left unsaid. They also speculate that the chemistry of the atmosphere of Mars may have changed dramatically – presumably because they think gases have interchanged. How would an electric discharge between the comet and Mars be seen?