The only form of life known to exist is life on Earth. This life relies on the availability of liquid water. However, life may have evolved under quite different physical and chemical conditions. A general consequence of life processes in planetary surfaces can, as on Earth, be a biogeochemical metamorphosis of the surface materials, which can further influence planetary evolution by modifying the atmosphere and the surface properties. The core activity of the planned cooperation is to investigate this class of questions with an emphasis on the catalytic role of interfacial water in planetary surfaces. Mars could be a first extraterrestrial test field.
Interfacial water can behave like bulk liquid far below 0° C (Möhlmann, 2004). This makes adsorbed and other interfacial water important for chemical, and hence possibly also biological, processes in planetary surfaces. Given the role of solutes in soils, unfrozen water is expected to have modified physical and biological properties. Moreover, biota produce antifreeze proteins that further modify the properties of the ice/water surface (Pertaya et al., 2007). Multi-layer adsorbed water films are known to have bulk water mobility with important consequences for solute and transport phenomena (Dash, 1975; Dash et al., 2006; Wettlaufer & Worster, 2006). The film thickness is extremely sensitive to the presence of solutes and hence such films are likely “houses” of biological activity on Mars. Indeed, Rivkina et al. (2000) have shown that at T ˜ -20°C, bacterial metabolism ceases at a level of about one monolayer. This is presumably related to the limited transport of nutrition and bacterial waste. In contrast, this transport seems to become effective at or above 2 monolayers. Importantly, water can be stabilized in mineral pores and may become available for endolithic microorganisms e.g., which could exist attached to internal surfaces. This socalled “biofilm” habitat in thin water layers is the prevalent mode of life of microorganisms on Earth, surviving and thriving under extreme conditions. Therefore, the chemical and hence possibly biological processes that are driven by interfacial water can ultimately contribute to the metamorphosis of planetary surfaces.