ORCID Profile
0000-0003-1130-9620
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Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-2810
Abstract: Aeolian and fluvial processes on Earth show significant interactions. Within terrestrial desert environments, analysis of ~200 locations has revealed that where ephemeral or episodic rivers flow across a dune field the predominant processes alternate between aeolian and fluvial, and that when rivers and dunes are active, they interact with one another. Avulsions can be major, with channels in the northern Kalahari having cumulative ersions of 10s of km. Considering Mars likely had an arid environment during the period of peak fluvial activity, the presence of fossilised Martian dunes, and observations by the Curiosity rover of fluvially altered aeolian deposits, it is apparent that Mars likely experienced simultaneous fluvial and aeolian processes, and periods of fluvial inactivity where aeolian processes persisted. At present, Martian aeolian and fluvial processes have only been studied independently, and their interaction has not been explored.Here we report the initial study by the Working group on Aeolian-Fluvial Terrain Interactions (WAFTI), based at the European Space Agency, which examines the effects of these processes in synergy under ancient Martian conditions, using a combination of modelling and geomorphological analysis. We hypothesise that these interactions could have implications for a number of Martian phenomena, for ex le: the prevalence of meandering inverted channel systems, the distribution of organic material, the discordance of Martian valley networks, and the sediment size and distribution of Martian rivers. In this study, we simulate the interactions between migrating dunes and different reaches of an active river channel, under ancient Martian conditions to determine the effects on the channel& #8217 s morphology and geometry.Our Martian Aeolian-Fluvial Interactions (MAFI) model is a landscape evolution model based on a coupled implementation of the Caesar-Lisflood fluvial model, and Discrete ECogeomorphic Aeolian Landscape model (DECAL) dunes model. It routes water over a Digital Elevation Model (DEM) and calculates erosion and deposition from fluvial and slope processes changing elevations accordingly. Aeolian material is discretized into slabs on the DEM, and slabs are moved across the space according to a set of simple rules.At EGU we will present the results of our simulations of aeolian and fluvial interactions on an inclined plane with a central channel and a continuously flowing Martian river. Typically on Mars, channels are housed within valleys with V or U-shaped cross-sections. Additionally, the topography of Mars is heavily altered by impact craters, many of which are sediment sinks. Finally, the profiles and immaturity of Martian valleys indicate that they were likely ephemeral/episodic, so flow was unlikely to be continuous. We, therefore, plan to expand our study to simulate the following: (1) simulate continuous flow for a DEM with a V-shaped valley and central channel (2) & #8220 & #8221 U-shaped valley and central channel (3) & #8220 & #8221 for a DEM with a crater present adjacent to the part of the valley (4) simulate episodic fluid flow with periods of no fluvial activity, but continued aeolian activity. Understanding these two major surface processes in synergy will aid in the reconstruction of Mars& #8217 ancient paleoenvironments in a way that has not previously been explored.
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-2831
Abstract: The surface of Titan displays evidence of fluvial and aeolian activity. Rainfall on Titan results in fluvial landforms (FLs), lakes, and seas. Unlike Earth, this rainfall is predominantly liquid methane. Titan& #8217 s surface conditions allow for liquid methane and ethane to be stable. Although the rainfall is primarily methane, this methane (liquid density ~424 kg/m3) can be photolyzed to form ethane (liquid density ~544 kg/ m3), resulting in lakes and rivers of ethane. Liquid ethane is more likely to be fed back into rivers and lakes by springs and play a formative role in the lower reaches of rivers. Changes in fluid density from the source (methane) to the terminus (ethane) of Titan& #8217 s rivers may affect the flow dynamics of the river. Methane fed rivers are likely episodically active since rainfall, which is concentrated in the poles, lasts 10-100 hours each Titan year (30 Earth years). Although precipitation is limited in the mid-latitudes, FLs have been observed in these regions. Titan is also covered by vast regions of active dune fields, primarily within the equatorial latitudes. They are composed of hydrocarbon and nitrile sand-sized particles forming from photochemical reactions in Titan& #8217 s atmosphere. Although observations of Titan are limited, interactions between rivers and dunes have been observed. Limited data availability means modelling fluvial and aeolian processes is one of the best methods to understand active and previously active processes on Titan. Here we report the initial study by the Working group on Aeolian-Fluvial Terrain Interactions (WAFTI), based at the European Space Agency, which examines the effects of these processes in synergy under Titan conditions, using a combination of modelling and geomorphological analysis. We hypothesise that these interactions could have implications for the distribution and planforms of Titan FLs. To simulate the interactions between fluvial and aeolian processes on Titan, we developed the Titan Aeolian-Fluvial Interactions model. This is a landscape evolution model based on a coupled implementation of the Caesar-Lisflood fluvial model, and Discrete ECogeomorphic Aeolian Landscape model (DECAL) dunes model. The Caesar-Lisflood fluvial model routes water over a digital elevation model and calculates erosion and deposition from fluvial and slope processes and changes elevations accordingly. The DECAL model is based on the Werner slab model of dunes, which simulates dune field development through self-organization. Several scenarios shall be modelled: (1) a continuous methane river, flowing in a straight channel with linear dunes migrating towards the channel parallel to its length (2) a continuous methane river flowing towards a dune field with crest lines perpendicular to the direction of flow (3) simulation scenario (1) but altered slope to represent the three different reaches (source, mid-reaches, and termination) of the channel and simulate for both methane and ethane flows by altering fluid density (4) simulation scenario (1) with an episodically active river and continually active dunes. The findings of these simulations may help understand the drainage patterns and distribution of FLs and methane/ethane across Titan.
Location: United States of America
No related grants have been discovered for Lisanne Braat.