Reactive gossans as iron-rich Mars analogue environments of astrobiological interest, Axel Heiberg Island, Nunavut

Arctic gossans are considered relevant Mars analogues due to their geochemical and mineralogical similarities. Forming in near-surface environments and known to preserve signs of life, they are of significant astrobiological interest. The Terrestrial Mineral Analysis by Remote Sensing (T-MARS) project investigated gossans at Expedition Fiord on Axel Heiberg Island (Nunavut, Canada) to (1) characterize their geochemistry and mineralogy, (2) understand their formation, (3) develop strategies for detecting similar features on Earth and on Mars, and (4) detect potential biosignatures. Orbital, drone-based, and ground imagery were used alongside laboratory analyses of surface and subsurface samples. Analytical techniques included X-ray fluorescence, X-ray diffraction, visible to thermal infrared spectroscopy, Raman spectroscopy and gas chromatography–mass spectrometry. Principal component analysis and supervised classification of orbital imagery effectively detected gossans. Field imaging provided outcrop-scale context. Elemental and spectroscopic analyses revealed mineral assemblages and oxidation gradients typical of gossans. Twenty-four minerals, organic carbon, and potential lipid biosignatures were detected. Our analyses suggest that gossans formed from the alteration of primary sulfides in diabase/gabbro sills or rafts, or from solubilized sulfates in nearby evaporites via a paleohydrothermal system. Diapirism likely facilitated fluid flow. Gossans continue to form contemporaneously within the active layer of the permafrost. The multi-scale approach used here proved effective and adaptable for planetary exploration. Future studies should aim to identify regions with gossan potential on Mars, which may require targeting faulted regions where fluids interacted with sulfur-bearing material. Future work should also aim to better understand the microbial communities inhabiting gossans. • An analog mission was conducted using multi-scale instruments relevant to Mars. • Gossans form from the alteration of igneous fragments or diabase and gabbro sills. • Diapir-related fracturing allows near-surface fluid migration for gossan formation. • Lipids and organic carbon preserved in acidic and oxidizing iron-rich environments. • Gossans on Mars may form in S and Fe-rich rocks near zones of structural disruption.