One of the features of the MAHLI microimager is that it has a set of LED lights around the lens aperture. The ultraviolet lights have now been tried out on one of the Yellowknife rocks Sayunei, which is a mixture of veining material and the surrounding sedimentary rock (see image).
Illuminating a sample with utraviolet light, at about 365 nanometres wavelength has the potential to cause the emission of light of greater wavelength e.g. green or red light. Fluorescence is caused when electrons in the mineral’s structure are temporarily lifted into a higher energy level and then fall back into a lower energy level, emitting light in the process.
Fluorescent minerals include calcium phosphate (apatite) and some sulphides which might be associated with alteration. X-rays can also cause fluorescence, but there is no way that we can detect them at the same time that APXS is analysing a surface.
Perhaps at some point in the mission noting fluorescence will fit in a missing piece in the jigsaw.
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