Evaluation of carbonate abundance in putative martian paleolake basins

Carbonate deposits have not been found so far on Mars, although there appears to have been sufficient water to have supported their formation. Many hypotheses have been proposed in order to explain this. In the present work we explore the possibility that the missed detection of carbonate deposits on the martian surface could be simply due to the fact that the concentration of carbonates, when mixed with other materials present in the sedimentary deposits, may be below the detection limit of the various instruments used so far in this search. In the present study we consider 21 putative paleolacustrine basins and use a sediment transport model to estimate the abundance of carbonates which could be present in the sediments deposited on the basin floor. In this way we find that for all the selected basins the estimated carbonate abundances are in general less than a few percent, and such values are below (or at best comparable to) the detection limits of the spectrometers flown around Mars during the recent space missions. Furthermore, applying the sediment transport model to the well studied Eberswalde crater, we conclude that the fluvio-lacustrine activity in this basin should have lasted for a period on the order of 10³–10⁴ years, in good agreement with previous work. Our results suggest that a hydrological cycle, able to move large volumes of water and to create relatively stable lakes, could have been active intermittently on Mars in the past, producing carbonate deposits that could escape detection by the instruments that have flown to date.