The Martian diurnal water cycle

Near-surface water (both in the regolith and atmosphere) represents a potentially important resource for the exploration of Mars. However, most analyses of these resources (cf Mellon and Jakosky, 1993, and references therein) hearken back to the seminal discussion of Martian volatiles by Leighton and Murray (1966) which assumed a planetwide average water vapor column of about 10 precipitable micrometers (pr-CM). This ignores considerable latitude, seasonal, and diurnal variations in water vapor. Similarly, previous high-resolution boundary-layer modeling of the diurnal water cycle (Zent et al., 1993) regarded the atmospheric column as controlling the soil conditions. Thus, the soil was initialized with some 2 kg m(-3) (corresponding to 20 pr-mu m cm(-1)) of water, causing the assumed atmospheric column to be filled in a matter of days. Global modeling of the Martian water cycle over a period of several decades (Houben et al., 1997), on the other hand, gives strong indications that the regolith water inventory is much smaller and that adsorption df water on this regolith dominates the lower atmospheric column. Presented here are diurnal boundary-layer calculations utilizing the one-dimensional Zent et al. (1993) model but which are initialized with the smaller Houben et al. (1997) estimated soil water inventories, for a variety of locations and seasons on Mars. (C) 1999 COSPAR. Published by Elsevier Science Ltd.