Planetary geomorphology
Our solar system is endowed with a fascinating family of planets and planetary bodies. Some are giant gas planets, like Jupiter, but most are smaller rocky or icy bodies. This group of smaller planets and satellites includes Earth. Intriguingly, the other bodies in this group share many geomorphological characteristics with Earth, pointing to many shared environmental processes: all have a history of planetary bombardment and cratering; some have atmospheres and show evidence of wind-sculpting, e.g.Venus, Mars and Titan; volcanism has been, or is currently, an important surface-producing agent on at least three, Venus, Mars and Jupiter’s satellite Io; Venus is the near-twin of Earth in size and has a dense atmosphere but its evolution has been very different from Earth’s, with crushing surface pressure, searing temperatures and aggressive atmospheric chemistry; several large satellites are shrouded in a mobile crust of ice overlying a global liquid ocean, e.g. Europa, Ganymede and Enceladus; the giant satellite Titan has a dense atmosphere that is chemically very similar to the Earth’s first atmosphere and it shows abundant evidence of a ‘hydrological’ cycle (although not involving water), including the presence of rivers and lakes; Mars, tantalizingly similar to Earth, is distinctly not an identical twin but it is relatively nearby and has been visited by many orbiters and landers that have shown it to be, or have been, very Earth-like at certain places and/or times or in specific process-domains. Given the close, but tantalizingly different, planetary evolution of Earth and Mars, the wealth of data available and the potential Mars offers for learning and research, including learning more about our planet, it will be the primary focus of this module, with an emphasis on the processes and landforms associated with water in all its phases (i.e. ice, liquid and vapour).
Currently, the best way to understand the geomorphology of another planet, and hence the environmental processes operating at the surface of that planet, is to find analogous landform assemblages here on Earth and to study as many of their genetic factors as possible. Many landforms and geomorphological assemblages on Mars are analogous to morphologies on Earth that formed in volcanic, aeolian, fluvial, lacustrine, marine, periglacial, glaciofluvial and glacial process environments. These include: volcanoes and lava; sand dunes and yardangs; rivers, gullies and river networks; lake basins and shorelines; extensive marine basins, seabeds and shorelines; rock glaciers and glaciers, patterned ground (polygons), sorted periglacial landforms, thermokarst and pingos. The discovery of these landforms on Mars, in high-resolution images of the surface, has led to the conclusion that volcanism, wind, liquid water and ice have collaborated to produce a very Earth-like planetary surface. However, the geomorphology of Mars is showing evidence of one or more recent major changes in Martian climate, possibly including brief periods when water recently became morphologically effective. The likely cause for such a change is orbitally-driven variability in the axial obliquity of Mars. The same process is a major factor behind the repeated cycles of glaciation experienced by Earth over the last 2 Ma. If this can be confirmed, it would have major implications for our understanding of climate and water on Mars and would tell us more about the processes of environmental change on Earth, including the feedbacks between climate forcing, global warming, cryospheric stability and the hydrological cycle. Many tailored field campaigns are active on Earth, with research agendas that are Mars-specific and targeted, for example, at parameterization of key morphologies as proxies for those key processes, i.e. climate change, cryospheric stability and the cycling of water from sources to sinks. Insights from these analogue studies should provide a better understanding of the relationships between landforms, surface materials (including chemistries) and the surface processes of both Mars and Earth. For that reason, this analogue approach to planetary geomorphology will be the focus of this module, both conceptually and methodologically.
Learning Outcomes:
Students will be introduced to the major areas of research in planetary geomorphology, the datasets available and the methodologies of planetary geomorphology, all with a special focus on the geomorphology of Mars. From working in and studying for this module students should gain an understanding of the diversity of planetary geomorphology and planetary evolution in our solar system.
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Planetary geomorphology
Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or HaDEA. Neither the European Union nor the granting authority can be held responsible for them. The statements made herein do not necessarily have the consent or agreement of the ASTRAIOS Consortium. These represent the opinion and findings of the author(s).
