The Power of Comparative Planetology to Decipher the History of Planetary Surfaces

Landforms, shaped by interactions between environmental fluids and geologic surfaces, encode information about hydrology, climate, and the overall environment that may be preserved over geologic timescales. Thus, understanding the mechanics of geomorphic and sedimentary processes that shape the landscapes of planets is key to deciphering their respective paleoenvironmental records. To date, the majority of mechanistic models for surface processes were derived from observations of modern Earth, where life thrives, and from scaled-down experiments. Numerical models help to probe wider parameter spaces than can be achieved on our planet, but they only contain the physical rules that they were designed to honor in the first place. However, the foreign parameter spaces spanned by other planets may lead to phenomena that we do not realize need to be included in our models – the unknown unknowns. Even Earth would have looked alien to any of us before the advent of macroscopic life, with a different atmospheric composition and different surface sedimentary dynamics for example. As a result, the applicability of existing models for surface processes is often limited to those systems that most closely resemble modern terrestrial conditions, impeding our ability to reliably decipher the environmental records of other planets and the early Earth. Flipping this paradigm, planetary bodies in our Solar System and beyond span a range of sizes, environments, and compositions that allow us to approach comparative planetology as a full-scale experiment, where other bodies offer a unique opportunity to develop more robust models and expand their applicability. Knowledge gained from the exploration of other planets not only contributes to our fundamental understanding of surface processes, but at times can feed back into our understanding of the Earth. In this presentation, I will illustrate how a dialogue between the Earth and planetary sciences can increase our ability to interpret the landscapes and rocks with three examples from our own Solar System – the formation of large eolian ripples under the thin martian atmosphere, the dynamics and record of unvegetated meandering rivers on the early Earth and Mars, and the alien organic-sediment cycle of Saturn’s moon, Titan.