Syn-tectonic Sedimentation in Valles Marineris, Mars

Post contributed by Dr Joel Davis, Department of Earth Sciences, Natural History Museum, UK

On Earth, the interplay between tectonics and sedimentation is commonplace. In regions such as Death Valley, USA, extensional tectonic processes have formed sedimentary basins, where the subsequent erosion of the landscape causes the formation of features such as alluvial fans. Alluvial fans are conical-shaped, sedimentary deposits usually formed by stream flows in upland regions. Later tectonic activity can lead to the deformation and relative uplift of these landforms. A new generation of alluvial fans may then form, overprinting the older generation and extending down to the new position of the basin floor.

To contrast, as most alluvial fans on Mars are found within impact craters, they do not show evidence of tectonic deformation. The alluvial fans hosted within the canyons of Valles Marineris appear to be an exception to this (Figure 1). Valles Marineris may have developed over billions of years by repeated episodes of normal faulting. In several regions of Valles Marineris, not only are alluvial fans found on the current floor, but remnants of such features are found on the canyon walls as well – perched several kilometres above the floor!

Figure 1: Faulted alluvial fan deposits in Coprates Chasma, Mars. (A) Oblique Context Camera (CTX) image of multiple generations of alluvial fan deposits, offset by faulting. Credit: NASA/JPL/MSSS. Inset shows High Resolution Imaging Science Experiment (HiRISE) image of bright-toned layering in fan margins. Topographic contour interval is 200 m. Credit: NASA/JPL/UoA. (B) HiRISE mosaic of C2 alluvial fan deposits on canyon floor, where surfaces contain distributary channels and paired ridges, cut by multiple faults. Youngest C3 fans superpose faults and are local to C2 fan apices. Credit: NASA/JPL/UoA. (C) Planform CTX mosaic of oldest (C1) alluvial fan deposits (perched terraces), which have been faulted and later eroded (orange line). NASA/JPL/MSSS. After Davis et al., 2021.


Jostling Pack Ice(ish) on Venus

Post contributed by Prof. Paul K. Byrne, Department of Earth and Planetary Science, Washington University in St. Louis, USA.

Venus is a tectonically tortured world (Image 1). Vast rift systems, widespread crustal shortening, and a crumpled terrain type, tessera, collectively attest to major tectonic activity on a world only a little smaller than Earth. In places, strains are spatially distributed; in others, extension or shortening is concentrated into narrow bands. And, where these bands intersect, they define a type of tectonic deformation on Venus that hasn’t been recognised before.

Image 1: A 1,100 km-wide, false-colour radar view of Lavinia Planitia, one of the lowland regions on Venus where the lithosphere has fragmented into blocks (purple) delineated by belts of tectonic structures (yellow). Image credit: Paul K. Byrne.


Ridged Plains on Europa Reveal a Compressive Past

Post Contributed by Dr. Erin Leonard, Postdoctoral Fellow at the Jet Propulsion Laboratory, California Institute of Technology

Jupiter’s icy moon Europa has a geologically young surface (60-100 million years old), as evidenced by the sparsity of large impact craters. Studying the surface features on Europa allows insight into how resurfacing may have given it a youthful appearance. The majority of Europa’s young surface is made up of Ridged Plains terrain. This terrain has not been extensively studied before because it appears as a smooth and relatively bland in the global-scale images. However, in the few high-resolution images returned by the Galileo mission in the early 2000s, the Ridged Plains are revealed to consist of numerous ridges and troughs that have a range of morphologies—from crisscrossing each other in various directions to orderly sets of parallel structures (Image 1). But how did these ridges and troughs form?


Image 1: A variety of examples of ridged plains on Europa. Note the linear to curvilinear systematic ridge traces in all examples: (A) observation E4ESDRKMAT02 at 26 m/pixel, (B) observation 19ESRHADAM01 at 66 m/pixel, (C) observation 12ESWEDGE_02 at 29 m/pixel, and (D) observation 12ESMOTTLE02 at 16 m/pixel.


Valley Networks on Venus

Posted by Dr. Goro Komatsu, IRSPS, Univ. G.d’Annunzio, Italy.  

(Re-posted from IAG Image of the Month, December, 2007)

“…excitement and pleasure in science derive not so much from achieving the final explanation as from discovering the fascinating range of new phenomena to be explained” (Baker and Komatsu, 1999).”

Networks on Venus

The Magellan spacecraft acquired SAR (Synthetic Aperture Radar) images of venusian surfaces at a spatial resolution range of about 100 m per pixel.


Vir-Ava Chasma, Venus

Posted by Les Bleamaster, Planetary Science Institute, Tucson, Arizona, USA.

(Re-posted from IAG Image of the month, July 2007)

This false color, three-dimensional perspective view over the Turan Planum of Venus shows the interaction of tectonic structures and volcanic processes along chasmata or “rifts.”


Foreground is approximately 400 km, with a vertical exaggeration of 8x.


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