Mars with water flows and pools

Images acquired by the camera of the Mars Global Surveyor spacecraft at spatial resolutions of a few meters make it possible to distinguish objects that may be related to existing sources of liquid water located on slopes, rather than to the shift of large masses of dry sand or rock falls. The availability of big reserves of sub-ground ice on Mars is now universally accepted. Although the presence of liquid water on the Martian surface is usually thought to be impossible because of low pressures and low mean temperatures, there is a sufficient number of lowlands on Mars where pressure exceeds the critical value, required for the existence of liquid water. The extended narrow gullies on slopes with tributaries were formed, most probably, by water streams. The structure of gullies has an unusual appearance, reverse of that of mountain rivers on Earth: gullies are broad in the upper part of a slope, narrow downslope, end with a thin stream, and disappear at the valley or crater floor. Both tributaries and the major channel seem to be directed uphill. The apparent paradox is explained by the interaction of a cooling stream with a very cold ground. Under low-temperature conditions, the conversion of liquid water to the ice phase should be considered in dynamics: the water released by the source comes in contact with a cold ground, partly soaks in ground, and freezes, forming an ice bed along which the stream moves further and continues to interact with ground. The distance from the source at which water completely disappears depends on the initial temperature of the source, its abundance, and the ground temperature. As regards the side structures, they are not tributaries but branches, which rapidly freeze. A high source debit and/or sufficiently high ambient temperature promote the formation on the valley floor of a small pond that accumulates water flows. The walls of this pond consist of frozen soaked ground and ice. Objects that might be small water reservoirs are detected in some new images of Mars. High concentration of sources of groundwater in two equatorial regions of Mars may serve as an indication to the location of places promising for searching traces of life. They may be attributed to ancient migration of Martian poles (Schultz et al., 1982).