Searching for Water on a cold dry Mars

Water on Mars Underlying the rationale for the search for extant water on modern Mars is the assumption that surface features record a history of flowing water. The strongest evidence for past water comes from the outburst flood channels which clearly document episodes of fluid escape and erosion, and long-distance sediment transport, largely in the Hesperian (pre 3.0 to 3.5 Ga according to revised Neukum and Hartmann dating). Additional evidence comes from sapped valley networks in the Noachian, individual sapped channels at other geological times, and from the geologically recent gullies of Malin and Edgett. The contacts originally identified by Parker are also often interpreted as evidence for a Boreal Ocean. In short, there is ample observational evidence for fluid-related features on Mars and conventionally Occam’s razor has been wielded in favour of water-based models despite some embarrassing paradoxes such as the lack of surface carbonates. Yet it should never be forgotten that water on Mars is an assumption, and one that does not match well with present surface conditions.