Seen from a mass and energy conservation angle, the first few mm or cm within and above the ground of a planet, almost unaffected by atmospheric mixing, see the most extreme gradients in temperature and composition. These gradients and the related exchange of mass and energy is of great importance for the ingestion of soil components, be they solids or volatiles, into a planet’s wider meteorological system. At PSSRI, the exchange of heat and volatiles between planetary surfaces and their environments is investigated.
This field is of interest for various reasons. The existence of past and present volatile reservoirs is amongst the prime goals for understanding the potential for life on Mars. A good understanding of the near-surface heat and volatile exchange processes is absolutely essential for estimating the depth to any current liquid water deposits and for understanding the history of liquid water on Mars. Water is not only a prerequisite for life and acts as a solvent for many chemicals needed in the biological cycle, its change of phase is also an important energy source. In addition, water is an important greenhouse gas, in fact the most important one on Earth.
In addition to water on Mars, the sublimation cycle of CO2 greatly influences the thermal environment within the soil; within the diurnal and annual cycle, CO2 ice can bind the grains in Mars’ soil together through sintering, which increases thermal conductivity of the soil whilst, on the other hand, making it less permeable for volatiles. This process could help to sustain subsurface volatile deposits (not only on Mars but also on the Moon. The surface-to air transfer of the greenhouse gases water, CO2 and methane in Earth’s, Mars’ (and also Titan’s) systems is an important factor in the understanding of climate change, and climate changes have also been suggested as a possible explanation for the cooling of the surface of Mars.
Planetary surfaces as the interfaces between solid bodies and their atmospheres (or exospheres) are usually approximated on large scales. There is a persistent exchange of mass and energy between the porous, granular ground and the atmosphere or exosphere – the interface is fuzzy rather than discrete and changes over time and it is the small-scale interactions at this fuzzy interface we are interested in.
This research is an integral part of the broader investigation of the Planetary Surfaces Group - a new interdisciplinary grouping within CEPSAR between members of PSSRI and Earth Sciences. The activities of revolve around studies of planetary surfaces and the processes that shape them, through the use of in-situ and remote sensing data, analogue field and laboratory studies, and mathematical models. Research interests within the group include:
• Formation and evolution of planetary surfaces
• Planetary surface heat flow
• Planetary surface/atmosphere interactions
• Geomorphological expressions of recent climate change on Mars
• Water and ice in the martian regolith
Surface of Titan - image courtesy of ESA/NASA, Univ. of Arizona