Inverted channels on Mars contain a record of fluvial processes as well as of the subsequent geochemical processes that have modified the deposits over time. Williams et al.  suggest that the channel deposits have become hardened relative to their surrounding sediments, presumably through cementation likely caused by near‐surface solute‐rich groundwater. This suggests an extension of aqueous processes beyond the period of widespread fluvial activity, perhaps through subsurface fluid flow or groundwater upwelling.
Citation: Williams, R. M. E., Moersch, J. E., & Fergason, R. L. . Thermophysical properties of Martian fluvial sinuous ridges: Inferences on “inverted channel” induration agent. Earth and Space Science, 5, 516–528. https://doi.org/10.1029/2018EA000402
—Benoît Pirenne, Editor, Earth and Space Science