The Keeper wrote:
^Um, it hasn't hit the ground yet. It appears to me it still falling from orbit, hasn't began striking the atmosphere yet. See the clouds far, far below.
Btw, the 4 "bubble trails" are captured here. 2 from the leading edge of the saucer and 2 rising up, (imo) between the nacelle struts from the engineering section. (Sorry it isn't HD)
To expand what I speculated in another thread (sorry, don't mean to spam), I don't know how much moisture would be that high in the atmosphere, but I'd guess that's condensation from the heat at those points on the saucer and nacelle.
As the ad showed, when the Enterprise is lower, smoke is billowing from those spots. The fires probably really took off when the atmosphere got thicker with oxygen to keep fueling them.