...is one example where very specific information about a complex chemical is provided by obvious spectral manipulation - not just selective absorbance/reflectivity, but converting e.g. UV to visible light at specific combinations of wavelengths. We use fluorescence techniques to identify hydrocarbons floating on the surface of the see and can discriminate spills of refined oils such as diesel and fuel oil from seepages of crude oil.

Some of the nuts have claimed they see fluorescence on Mars (because of perceived imbalance of HST green vs red and blue channelss), but their argument is spurious.