All posts tagged tectonics

Regional Impact Crater Mapping of Saturn’s moon Dione

Post contributed by Dr. Sierra Ferguson. Postdoctoral Researcher, Department of Space Studies, Southwest Research Institute, Boulder Colorado, USA.

Dione is one of Saturn’s many photogenic “mid-sized” icy moons, first visited by the Voyager mission in 1980. Most well-known for its system of bright scarps/troughs on the trailing hemisphere of the moon (aka the “wispy terrain”, Image 1), Dione is host to a wide range of interesting surface and subsurface features such as impact craters, tectonics, and potentially a subsurface ocean. Models of the formation of the Saturnian satellites have frequently placed their formation ages at ~ 4 billion years ago, roughly around the same time that Saturn itself formed. However, recent modeling of the orbital dynamics of the system have shown that the inner moons (Mimas, Enceladus, Tethys, Dione, and Rhea) may in fact be much younger, with the youngest potential formation age only 100 million years ago. One way to examine the surface ages, and the potential formation age of Dione, is through the analysis of impact crater distributions. We utilized images from NASA’s Cassini spacecraft to examine the sources of craters on Dione and what they mean for the ages of Saturn’s satellites and the evolution of Dione’s surface (Ferguson et al., 2022b).

Impact craters are very common geologic feature on planetary surfaces. We can analyze their distributions to examine their origins, and model the surface age of a mapped region. A lack of impact craters is often interpreted to be a result of crater erasure by geologic resurfacing process (i.e., volcanism, mass wasting, additional cratering). By mapping the observed craters on Dione, we are able to characterize the bombardment environment at Saturn as well as the modification history of Dione’s surface.

Image 1: Cassini ISS-NAC image of Dione’s wispy terrain area. This image provides context for the craters on the surface as well as the relationship of the craters to the tectonic features observed on the surface. Image credit NASA/JPL/SSI, PIA 18327 (https://photojournal.jpl.nasa.gov/catalog/PIA18327)

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by fegbutcher on September 1, 2022  •  Permalink
Posted in Saturn Moons
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Posted by fegbutcher on September 1, 2022

https://planetarygeomorphology.wordpress.com/2022/09/01/regional-impact-crater-mapping-of-saturns-moon-dione/

Tectonic evolution of Ganymede’s leading hemisphere

Post contributed by Dr. Costanza Rossi, Astronomical Observatory of Padova, Italian National Institute for Astrophysics

During their 1979 flybys of the Jovian system, the Voyager probes revealed to us abundant evidence of global-scale structures on the icy satellite Ganymede (Image 1), showing that tectonic activity played a key role during its geologic history. Ganymede’s puzzling surface covers an internal liquid ocean and is characterized by two main geological units, the dark and light terrains (> 4 billion and 2 billion years old, respectively; Patterson et al., 2010), which are shaped by a complex tangle of linear to curvilinear morpho-tectonic structures (Image 1). There are brittle structures called furrows within the dark terrain, and grooves within the light one, which (apparently) represent disconnected deformation histories. Impact cratering processes affected the dark terrain by forming furrows with graben-like morphologies, which are interpreted as remnants of a multi-ring basin formed by a giant ancient impact (e.g., Prockter et al., 2000). On the other hand, the light terrain formed at the expense of the dark one, as a result of strong tectonics that formed the grooves (e.g., Pappalardo et al., 1998). Although extension is considered as the main process for the groove formation, it is assumed that strike-slip has been also pivotal during their development (Cameron et al., 2018; Rossi et al., 2018). The lack of pure compressional structures still represents one of the open enigmas of the tectonics of Ganymede. Ganymede’s tectonic-related landforms potentially represent pathways connecting the surface with the underlying ocean, and their investigation is pivotal to understand their possible development and interconnection at depth (e.g., Lucchetti et al., 2021), their evolution, and the endogenic processes responsible for their formation.

Image 1: Orthographic projection of the leading hemisphere of Ganymede (Voyager/Galileo global mosaic of Kersten et al., 2021). The dark squares show the location of Image 2 and the white square shows the location of Image 3.

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by fegbutcher on August 1, 2022  •  Permalink
Posted in Ganymede, Jupiter's Moons
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Posted by fegbutcher on August 1, 2022

https://planetarygeomorphology.wordpress.com/2022/08/01/tectonic-evolution-of-ganymedes-leading-hemisphere/

Antipodal Terrains on Pluto

Post contributed by C. Adeene Denton, Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, USA.

Antipodal terrains are unusual regions of hilly, lineated, or otherwise disrupted terrain that are on the direct opposite side of planetary bodies to large impact basins. These mysterious terrains have been observed at the antipodes to the Caloris basin on Mercury and the Imbrium basin on the Moon, where their formation is considered to be indicative both of the impact’s size and the specificities of the planetary body’s interior structure. Recent revisiting of data from the New Horizons spacecraft revealed an unusual region of disrupted and lineated terrain on Pluto’s far side that is roughly antipodal to the massive Sputnik Planitia basin, the feature sometimes referred to as “Pluto’s Heart” (Image 1). If the lineated terrain is indeed connected to the large impact believed to have formed Sputnik Planitia, then the two geologic features offer a new and unusual way to probe Pluto’s interior: seismology through giant impact.

Image 1: Comparison of Pluto’s nearside (left) and farside (right) with Sputnik Planitia and its proposed antipodal terrain indicated. The location of Image 3 is also indicated. Images modified from full-scale planetary images taken by the New Horizons spacecraft, via NASA/JHUAPL/SWRI.

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by fegbutcher on April 1, 2021  •  Permalink
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Posted by fegbutcher on April 1, 2021

https://planetarygeomorphology.wordpress.com/2021/04/01/antipodal-terrains-on-pluto/

Polygonal Impact Craters on Miranda, Charon, and Dione

Post contributed by Dr. Chloe B. Beddingfield, The SETI Institute and NASA Ames Research Center

Some impact craters are classified as polygonal impact craters (PICs), which have at least one straight rim segment, as shown in Image 1. The morphologies of PICs are shaped by pre-existing, sub-vertical structures in the target material, such as normal and strike-slip faults, joint sets, and lithologic boundaries. Because the straight rim segments of PICs only form where pre-existing structures are present, PIC morphologies can be used to analyze fractures that are buried by regolith or too small to be seen in available spacecraft images. On the icy Uranian moon Miranda, PICs are widespread across its southern hemisphere, which was imaged by the Imaging Science System (ISS) onboard the Voyager 2 spacecraft. Some of these PICs reveal previously undetected fractures that suggest Miranda has experienced multiple periods of tectonic activity.

Image 1: Examples of two PICs identified on the Uranian moon Miranda. Black arrows indicate the straight rims of these PICs. The Voyager 2 ISS image mosaic shown here includes the following images, from top to bottom: c2684620 (light blue box), c2684629, c2684617 (dark blue box).

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by fegbutcher on October 1, 2020  •  Permalink
Posted in Pluto Moons, Saturn Moons, Uranus Moons
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Posted by fegbutcher on October 1, 2020

https://planetarygeomorphology.wordpress.com/2020/10/01/polygonal-impact-craters-on-miranda-charon-and-dione/

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?

LeonardFigure1

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.

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by Tjalling de Haas on April 1, 2020  •  Permalink
Posted in Europa, Experiment
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Posted by Tjalling de Haas on April 1, 2020

https://planetarygeomorphology.wordpress.com/2020/04/01/ridged-plains-on-europa/

Enigmatic Normal Faults on Ceres

Post by Kynan Hughson, Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, USA.

Since March of 2015 NASA’s Dawn spacecraft has been actively exploring the main asteroid belt’s largest member and only dwarf planet in the inner solar system: Ceres. Situated around two fifths of the way between the orbits of Mars and Jupiter, Ceres is gargantuan compared to its neighbors. With a mean diameter of ~946 km (approximately the width of the state of Texas) and a bulk density of ~2.16 g/cm3 it comprises around one third of the mass of the entire main belt. Dawn’s continuing examination of this unique object since March 2015 has revealed a geologically diverse world covered with geomorphological features common to both rocky inner solar system planets and icy outer solar system satellites (e.g. Bland et al., 2016; Schmidt et al., 2017; Fu et al., 2017). These observations have exacerbated Ceres’ refusal to be neatly categorized as either a rocky or icy planet.

narSulcusRotation

Image 1: A rotating aerial view of Nar Sulcus (centered at approximately 79.9 °W, 41.9 °S). Note the two nearly perpendicular sets of fractures. In particular, note the imbricated blocks within the longer fracture set. The longer fracture set is approximately 45 km long, and the deepest valleys are ~400 m deep. This scene was created using a stereophotogrammetrically (SPG) derived elevation model (vertical resolution ~15 m) and high resolution (~35 m/pixel) Dawn framing camera mosaics (Roatsch et al., 2016a; Roatsch et al., 2016b), which are available on the Small Bodies Node of NASA’s Planetary Data System.

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by Tjalling de Haas on July 1, 2018  •  Permalink
Posted in Ceres
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Posted by Tjalling de Haas on July 1, 2018

https://planetarygeomorphology.wordpress.com/2018/07/01/enigmatic-normal-faults-on-ceres/

Pit chains on Enceladus

Post contributed by Dr. Emily S. Martin, Research Fellow, Center for Earth and Planetary Studies, National Air & Space Museum, Smithsonian Institution.

Pit chains are linear assemblages of circular to elliptical pits and have been observed across the solar system. Pit chains have been found on Venus, Earth, Mars, Phobos, Eros, Gaspra, Ida, and Vesta. Across the solar system, pit chains may form through a variety of mechanisms including the collapse of lava tubes, karst, venting, extensional fracturing, or dilational faulting. Saturn’s tiny icy moon Enceladus is the first body of the outer solar system on which pit chains have been identified. Enceladus is only 500 km in diameter and is best known for its warm south pole and its watery plume emanating from prominent ridges known as tiger stripes. The source of the plume is likely a global liquid water ocean beneath an icy shell.

Image1

Image 1: The morphology of pit chains across the solar system. a. Eros from NEAR. Image no. 135344864. b. Phobos. Image PIA10367. c. Albalonga Catena, Vesta. d. Venus. Right-look Magellan data near 13°S, 112°E. e. Kilauea Volcano, Hawaii centered at 19.3909°N 155.3076°W. Image taken 12/06/2014, acquired from Google Earth on 04/20/2016. f. Ida, modified from image PIA00332. g. Gaspra, modified from Galileo image PIA00332. h. Pit chains in north-eastern Iceland centered near 65.9902°N and 16.5301°W. Image taken on 7/27/2012, acquired from Google Earth 04/20/2016. i. Pit chains on Mars from the Mars Global Surveyor Mars Orbiter Camera, centered near 6.5398°S and 119.9703°W on the flank of Arsia Mons. Image PIA02874.

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by suja82 on August 30, 2017  •  Permalink
Posted in Saturn Moons
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Posted by suja82 on August 30, 2017

https://planetarygeomorphology.wordpress.com/2017/08/30/pit-chains-on-enceladus/

It is Mercury’s fault(s)…

Post contributed by Valentina Galluzzi, INAF, Istituto di Astrofisica e Planetologia Spaziali (IAPS), Rome, Italy

Any celestial body that possesses a rigid crust, be it made of rock (e.g. terrestrial planets, asteroids) or ice (e.g. icy satellites), is subject to both endogenic and exogenic forces that cause the deformation of crustal materials. As a result of the mass movement, the brittle layers often break and slide along “planes” commonly known as faults. In particular, tensional, compressional and shear forces form normal, reverse and strike-slip faults, respectively. On Earth, plate tectonics is the main source of these stresses, being a balanced process that causes the lithospheric plates to diverge, converge and slide with respect to each other. On Mercury, there are no plates and therefore the tectonics work differently. Instead its surface is dominated by widespread lobate scarps, which are the surface expression of contractional thrust faults (i.e. reverse faults whose dip angle is less than 45°) and this small planet is in a state of global contraction.

image1

Image 1. Endeavour Rupes area on Mercury, image is centred at 37.5°N, 31.7°W. Top: MESSENGER MDIS High-Incidence angle basemap illuminated from the West (HIW) at 166 m/pixel. Bottom: MESSENGER global DEM v2 with a 665m grid [USGS Astrogeology Science Center] on HIW basemap, the purple to brown colour ramp represents low to high elevations, respectively. Endeavour Rupes scarp is high ~500 m. For scale, Holbein crater diameter is approximately 110 km.

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by suja82 on October 28, 2016  •  Permalink
Posted in Mercury
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Posted by suja82 on October 28, 2016

https://planetarygeomorphology.wordpress.com/2016/10/28/it-is-mercurys-faults/

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