WATER AS A GEOLOGIC RESOURCE IN SUPPORT OF PLANETARY EXPLORATION

Water in all of its physical states has long been considered one of the most vital resources for both research and in situ resource utilization (ISRU) within the Solar System. It has been firmly established that tracing the various pathways of water within Planet Earth and perhaps on Mars can yield significant insights into the chemical and potential biological evolution of such objects. Climate and sedimentary records are both established and preserved in the presence of water. Within the accessible Solar System, finding those physical niches where water can persist in its liquid state has emerged as one of the key "quests" within Astrobiology. However, the question can be broadened to include water as a resource to amplify the possibilities associated with planetary exploration. Studies have shown that available water could serve as an excellent source of hydrogen for propellant, for fuel cells, and as a key ingredient in many strategies involving space radiation shielding of future deep space human explorers. What are the prospects for water as a resource within the Solar System? Ice has been putatively identified in permanently shadowed polar craters on Mercury. Water could have been a major factor in the onset of the atmospheric greenhouse on Venus. Water is of course the key molecule here on Earth for life, climate, chemical evolution of the crust, and weathering. On Mars, the role of water may mimic aspects of the geo-hydrological cycle of Earth and we know there are ice-water polar caps and atmospheric water vapor. Water is possibly preserved within lunar soils in permanently shadowed areas on the Moon, although more detailed quantification is required if it is to be inventoried. As one moves radially beyond the orbit of Mars, water takes on an increasingly significant role. Large satellites of Jupiter including Europa may harbor sub-crustal water oceans ("aquifers at oceanic scales"), and the role of water in the formation of the crusts of the so-called icy satellites of the outer Solar System is well-known. Thus, it is safe to say that learning to study and use the available water within the Solar System will not only resolve key questions, but also permit clever amplification of the activities we seek to undertake, including human exploration.