Revisiting the identification of methane on Mars using TES data

Abstract

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 CH 4 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.

Statistical analysis of Curiosity data shows no evidence for a strong seasonal cycle of martian methane

“…In addition, a weak signal from the 7.7 µm band in data from the Thermal Emission Spectrometer (TES) on the Mars Global Surveyor orbiter purportedly showed seasonally variable methane at levels of 0-30 ppbv (Fonti and Marzo, 2010). However, the data were revisited and the result was shown to be consistent with a non-detection (Fonti et al, 2015).…”

Methane on Mars: New insights into the sensitivity of CH4 with the NOMAD/ExoMars spectrometer through its first in-flight calibration

“…Hence, at present, no space mission has been really tailored to the extensive detection and quantification of trace gases, apart from the very specific issue of methane detection in the Martian atmosphere, which has generated heated debate in the scientific community (see e.g. Fonti et al, 2015;Formisano et al, 2004;Krasnopolsky et al, 2004;Mumma et al, 2009).…”

Background levels of methane in Mars’ atmosphere show strong seasonal variations

“…From Mars orbit, the Planetary Fourier Spectrometer (PFS) on the Mars Express spacecraft measured a global average abundance of 15 ± 5 ppbv from 2004 to 2010 (17,18). The Thermal Emission Spectrometer on the Mars Global Surveyor spacecraft measured abundances ranging from 5 to 60 ppbv (19), although the claims of local variations were later withdrawn (20). Published maps of PFS data (18) at Curiosity's landing site in Gale crater (4.5°S, 137°E) show an increase over 1 year from~15 ppbv in Autumn to~30 ppbv in winter.…”