Blanc SIMI 5 - Blanc - SIMI 5 - Physique subatomique et théories associées, astrophysique, astronomie et planétologie

Characterization of the EXtra-terrestrial environments of Mars and Titan by the Observation and simulation of DUNEfieldS – EXO-DUNES

EXO-DUNES

Characterization of the EXtra-terrestrial environments of Mars and Titan by the Observation and simulation of DUNE fieldS

Understand planetary climatic and sedimentary environment by the observation and simulation of planetary and terrestrial dunes

The scope of the EXODUNES project is to document planetary dune features as well as the atmospheric and sedimentary processes that created and shaped them. <br />It is long known that it is possible to derive a set of environmental and dynamical parameters, such as atmospheric and sediment densities, grain size, depth of the atmospheric boundary layer, mean wind direction…, from the morphology and orientation of dunes. <br />However, the observation of dune shapes and orientations alone is not sufficient to resolve the ambiguity between the combined roles of the atmospheric flows and the grain mechanical properties. Transport laws, wind regimes and sediment properties being highly non-linearly coupled, this exercise turns out to be an inverse problem of a vast intrinsic complexity. EXO-DUNES is therefore a highly collaborative and interdisciplinary project, bringing together researchers with interests in planetary dunes and with diverse backgrounds in image analysis, experimental researches, modeling, and terrestrial analogue studies.

We propose to study in details the dunes of Mars and Titan, with the help of Earth’s relevant analogs, when available. The objective of this project is to develop new quantitative methods in order to disclose the fundamental information about the nature of the sediment and the atmospheric wind regimes that are contained in the morphology, size and orientation of dunes. We identify three specific, but essential questions about the morphogenesis and evolution of dunes on Mars and Titan: (1) what is the origin and role of the inter-grain cohesion? (2) what is the role of topography? (3) what are the role of the variability of the wind in intensity and direction?
The first part of this project is to analyze images and topography of planetary dunes on Mars and Titan and to quantitatively study their morphodynamics (composition, shape, orientation, migration direction and velocity…), in comparison with Earth’s analogues. The second part will consist in experimental and numerical researches on planetary climates and dune morphodynamics. Experiments and numerical simulations will be gradually fed by the observations and will be conducted in parallel, in a mutual beneficial interaction. At the end, we plan to have a detailed description of the climatic (wind regimes and variability) and sedimentary conditions (role of cohesion and topography) that shaped Mars and Titan’s dunes. This will provide important feedbacks on the global understanding of the physics of dunes on Earth.

Among the numerous results we add the opportunity to published over the period of the EXODUNES project, we selected a few major advances that significantly improve our understanding of planetary and terrestrial dune systems. First of all, we developed and validated a new theory that is able to predict the mode of dune growth in a multi-directional wind regime for two end-members of sand availability (infinite and null) and to calculate the associated orientation of their crest. This theory has been built with the help of laboratory and numerical experiments. It then paved the way to the very first terrestrial and planetary applications of the dune inverse problem in the context of complex multi-modal wind regimes. It allowed us to reconstruct sediment transport and constrain wind conditions from the morphology and dynamics of linear dunes dune in the several terrestrial deserts, but also on Mars and Titan.

Following the pioneering and promising results of our work, validating our methodology and tools, we intend now to proceed to the next steps: (1) test and calibrate the theory for dune orientation with numerical simulations and field campaigns in China, (2) pursue the experimental investigation of the transition between the different dune morphologies with a new experimental setup, (3) map the martian dunes and investigate the origin of their orientation in the light of the new theory for dune orientation, (4) quantify the growth rate of terrestrial and martian ‘finger’ dunes and the correspond sand fluxes, (5) develop a numerical model for studying the dynamics of icy dunes experiencing sublimation/condensation cycles.

The production associated to this ANR project primarily consists in regular and numerous scientific articles (32 in total), most of them in collaboration with one or more partners (13 multi-partner articles, 19 mono-partner articles), accounting for more than 200 citations and a h-index of 9. The subjects of these articles are partitioned between all the activities proposed within the framework of the EXODUNES ANR project: theory and experimental and numerical simulations of dune morphodynamics under realistic wind regimes, characterization of terrestrial and planetary dunes (composition, shape, crest orientation), applications to terrestrial and planetary dune field and desert dynamics, inversion of dune dynamics for the evaluation of climatic and sedimentary environments. We also participated to the organization of mumerous session on planetary dunes in international conferences between 2015 and 2018 (EGU, AGU, ICAR)and organized in November 2016 in Paris the International Titan Surface Meeting (80 participants).

The scope of the EXO-DUNES project is to document dune features as well as the atmospheric and sedimentary processes that created and shaped them on Mars and on the Saturn’s moon Titan.

Thanks to the actual programs of extensive observation and exploration of Mars and Titan, our knowledge of these planetary bodies has greatly improved. Atmospheric phenomena and landscapes on Mars and Titan bear striking resemblance with those on Earth. In particular, extensive dune fields were observed on these distant bodies, showing that dunes can form throughout the solar system under extremely various planetary environments. Dunes provide a powerful tool to investigate the sedimentary and climatic history of arid and semi-arid environments (such as on Earth deserts, and more globally on Mars and Titan).

Mars and Titan have both “exotic” environments, but only subtle differences in dune morphologies compared to terrestrial standards. Martian dunes are thought to be formed in frozen environments and their morphogenesis and evolution should be, at least partially, controlled by surface and sub-surface processes, such as local topography, volatile concentration in the sediment and frost/defrost cycles. Farther away from the Sun, the origin and morphogenesis of Titan’s dunes is still poorly understood, but the climate of Titan and the nature of the hydrocarbons “grains”, suggest that the inter-grain cohesion may play a major role. However, despite intensive studies of planetary dunes, many questions regarding their origins, composition, morphology, age and dynamics under present and past climatic conditions remain unanswered. Hence, Mars and Titan provide a unique opportunity to constrain dune morphodynamics under extreme environments and to improve in turn our current understanding of terrestrial atmospheric and surface processes.

We propose to study in details the dunes of Mars and Titan, with the help of Earth’s relevant analogs, when available. The objective of this project is to develop new quantitative methods in order to disclose the fundamental information about the nature of the sediment and the atmospheric wind regimes that are contained in the morphology, size and orientation of dunes. We identify three specific, but essential questions about the morphogenesis and evolution of dunes on Mars and Titan: (1) what is the origin and role of the inter-grain cohesion? (2) what is the role of topography? (3) what are the role of the variability of the wind in intensity and direction?

However, the observation of dune shapes and orientations alone is not sufficient to resolve the ambiguity between the combined roles of the atmospheric flows and the grain mechanical properties. Transport laws, wind regimes and sediment properties being highly non-linearly coupled, this exercise turns out to be an inverse problem of a vast intrinsic complexity. EXO-DUNES is therefore a highly collaborative and interdisciplinary project, bringing together researchers with interests in planetary dunes and with diverse backgrounds in image analysis, experimental researches, modeling, and terrestrial analogue studies.

The first part of this project is to analyze images and topography of planetary dunes on Mars and Titan and to quantitatively study their morphodynamics (composition, shape, orientation, migration direction and velocity…), in comparison with Earth’s analogues. The second part will consist in experimental and numerical researches on planetary climates and dune morphodynamics. Experiments and numerical simulations will be gradually fed by the observations and will be conducted in parallel, in a mutual beneficial interaction. At the end, we plan to have a detailed description of the climatic (wind regimes and variability) and sedimentary conditions (role of cohesion and topography) that shaped Mars and Titan’s dunes. This will provide important feedbacks on the global understanding of the physics of dunes on Earth.

Project coordination

Sébastien RODRIGUEZ (Astrophysique, Instrumentation et Modélisation) – sebastien.rodriguez@cea.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

MSC Matière et Systèmes Complexes
IPGP Institut de Physique du Globe de Paris
CEA/IRFU/AIM Astrophysique, Instrumentation et Modélisation

Help of the ANR 621,267 euros
Beginning and duration of the scientific project: December 2012 - 48 Months

Useful links

Explorez notre base de projets financés

 

 

ANR makes available its datasets on funded projects, click here to find more.

Sign up for the latest news:
Subscribe to our newsletter