The presence and variability of methane in the Martian atmosphere has been investigated
by several authors and spurred a lively discussion. In this context, we address our
previous inference of spatial and temporal CH4 variability identified from Mars Global Surveyor
Thermal Emission Spectrometer measurements which was used to suggest the possible
existence of a martian methane cycle. The importance of the topic requires a clear
assessment of such variability to correctly comprehend the possible production and
destruction mechanisms of Martian methane. It is therefore important to carefully revisit
previous results from a different perspective to confirm them before they are used for
further investigations. We here describe in detail a new procedure used to validate these
earlier Thermal Emission Spectrometer measurements and thoroughly analyze the results
obtained with the revised procedure. In spite of our efforts of defining an efficient data
analysis procedure, we have not been able to either confirm or refute the existence of the
spatial and temporal variability of methane. Nevertheless, our work has produced new
interesting tools, which, with the necessary adaptation, can be of some aid in processing
and interpreting planetary spectra and, in general, for all the other cases requiring a
preliminary selection of data included in very extensive datasets, which are difficult to
be efficiently treated with traditional techniques
