The ratio of pre- to post-impact ultraviolet/visible light data. Each line shows a individual ratio of scans starting with earlier times (pre-impact) at the bottom, and later times, moving up. The general increase over time is the result of sunlight reflecting off dust grains in the ejecta cloud. The sharp vertical features which appear shortly after impact, indicated in the shaded blue area, are the emission lines associated with OH. The eight, or strength, of these lines are related to the amount of OH, and hence water, present in sunlight.