Magnetic survey in Rio Tinto area: a Mars analogue.

Rio Tinto and Odiel are part of the fluvial system of the Iberian Pyritic Belt (IPB), so far the largest massive sulfide deposits found on continental crust on Earth. The extreme geochemical characteristics of Rio Tinto revealed this area as one of the most important geochemical Mars analogues on Earth. Its exotic mineralogy provides a good environmental analog for Hesperian/Teiikian mineral deposits on Mars, [1, 2, 3], and thanks to that, it is a unique place for developing and testing instruments for future planetary missions. Robotic vehicles and the recent technological demonstration of Ingenuity on Mars open up the possibility of using the powerful and non-destructive geophysical tool of magnetic surveys at different heights, for the investigation of surfaces and subsurfaces of planetary bodies. We explore IPB area Odiel-San Platón, were both jarosite (a key mineral from the Teiikian era of Mars) and important outcrops of Manganiferous Formation of the IPB are accessible. Manganese is a key element to support a putative microbial metabolism on Mars, but both acidic alteration of the rocks in this area and the low magnetic signal of manganese rich minerals, make the magnetic signature of the rocks, a challenge to be detected. We identify manganese-rich areas and minerals thanks to its magnetic signal, both in the field and with a detailed magnetic characterization of rock samples using a Vibrating Sample Magnetometer. In this research, we have done a magnetic survey and taken geological samples in field campaigns in 2018 and 2025. We propose a methodology which comprises an analysis of the morphology using images, magnetic field surveys, rock sample magnetic characterization, and simplified models for the interpretation of geological structures on the field. This methodology is applied successfully to the study of different areas of the Iberian Pyritic Belt, representative of the Martian landing sites mineralogy, as a preparatory action prior to the exploration of the planetary bodies’ surfaces.