MIKE MOSS SAYS:      Carol,   it seems likely that you saw a typical jet aircraft contrail, but happened to look up on a night when bright moolight made it plainly visible. We probably tend to notice fewer contrails at night because of a variety of factors - on many nights there are either obscuring clouds, or a lack of moonlight when clouds are absent, or we simply spend most of our time under a roof, and finally that later at night there are fewer aircraft aloft.