Characterizing the Dynamic Activity of Martian Mega-ripples and Transverse Aeolian Ridges

SCIENTIFIC MOTIVATION: Wind has been an enduring geologic agent throughout Mars’ history with the presence of aeolian bedforms across a range of sizes and morphologies. Many of these aeolian bedforms are enigmatic as compared to classical terrestrial bedforms. For example, the origin of moderate-scale (10-100 m spacing), light-toned Transverse Aeolian Ridges (TARs) has been long debated as large ripples or small dunes despite their near ubiquitousness. Similarly, smaller meter-scale dark-toned ripples (DTRs) generally do not form on Earth, implying an unique martian process is involved. Whereas the consensus view has been that TARs are dormant or inactive under current climatic conditions, orbital and surface observations show DTRs are migrating on Mars today. However, the size range in between these commonly cited bedform populations (5-20 m spacing and ~1-5 m tall) have been largely unexplored and generally assumed to be inactive like TARs. We term these intermediate-scale bedforms as mega-ripples based on their greater dimensions and brighter crests than DTRs, where we infer the latter is the results of a coarser grain size component.
New observations of decameter-scale bright bedforms, or mega-ripples, extend the known size range of migrating aeolian bedforms in the contemporary Martian climate regime. These mega-ripples also migrate, similar to smaller dark-toned ripples and larger sand dunes. This scale overlaps with enigmatic bedforms described as TARs. Additionally, the proposal team has recently presented the surprising result that certain bedforms characterized as small TARs may also be migrating. Because of the successes of the High Resolution Imaging Science Experiment (HiRISE) providing long-baseline (up to 6 Mars years) multi-temporal images, there is a timely opportunity to conduct data analysis in this area of research, which may prove vital in unlocking the secrets of Mars’ aeolian processes.

SCIENTIFIC OBJECTIVE: This proposed MDAP would test the following hypothesis, while enhancing the scientific return from current missions to Mars.

Overarching Hypothesis: Certain intermediate-scale aeolian bedforms on Mars, such as mega-ripples and TARs, are migrating in the current climate and can be identified based on their boundary conditions and proximity to high sand flux areas.

To achieve the primary objective and test this hypothesis this proposal has several tasks.

Task 1a: Assess the current inventory of moderate and high sand flux dunes sites with PDS released HiRISE Digital Terrain Models (DTMs) and orthoimages for initial evaluation of mega-ripple and TAR mobility.

Task 1b: For 20 sites with preexisting DTMs and known or suspected active mega-ripples/TARS identified from Task 1a, orthorectify long-baseline observations using SOCET SET photogrammetry software.

Task 2: Using the data products generated from Task 1b, quantify mega-ripple and TAR migration rates, directions, and volumetric sediment fluxes. Assess their overall contribution to the local aeolian system budget.

Task 3: For sites of active mega-ripple and TARs, assess local and regional boundary conditions, such as topographic, thermophysical, and seasonal properties.

PERCEIVED SIGNIFICANCE OF THE PROPOSED WORK: Achieving the science tasks listed above will advance the current state of knowledge of aeolian sediment transport and contemporary landscape evolution. The proposed research will provide detailed insight (where/when, and how/why) into the temporal and spatial aspects of ripple, mega-ripple, and TAR transport rates and sediment fluxes. Additionally, this research is in concordance with the Mars Exploration Program, as it addresses the following items in the current goals document (MEPEG, 2018) A3.1) Identify and characterize processes that are actively shaping the present-day surface of Mars..