Image and caption contributed by Rosaly Lopes, Jet Propulsion Laboratory, California Institute of Technology, California, USA, Randy Kirk, US Geological Survey, Astrogeology Science Center, Flagstaff, Arizona, USA and Mary Bourke, Geography, Trinity College, Dublin, Ireland.
Data from the Cassini mission have revealed that Titan is a planetary body where the interior, the surface, and atmospheric processes interact to create and modify landforms (Loppes et al, 2010). In terms of recent surface processes, Titan is one of the most earth-like bodies in our solar system. Landforms include the largest area of aeolian dunefields in our solar system (e.g., Radebaugh et al., 2008), lakes (e.g., Stofan et al., 2006), fluvial channels (e.g., Langhans et al., 2012), mountains (e.g., Radebaugh et al., 2007), and features that have been interpreted as volcanic (e.g., Lopes et al., 2007).
Image 1: The RADAR (SAR) images in black and white over a false-color mosaic of VIMS data. The globe at upper left shows the location of the map on Titan (arrow). The white lines show the approximate boundaries of the perspective view in Image 2.
Images from the SAR swaths in the T25 and T28 flybys show a region which is bright at radar wavelengths, except for the dune field that appear as linear, radar-dark features in the middle of the image (Image 1). At the top of the image is a mountain, Erebor Mons, interpreted to be cryovolcanic in origin. SAR data from these two flybys were used to produce the DEM (Image 2). The region near bottom center of the map, formerly known as Sotra Facula (centered at 39.8W, 12.5 S) was thus named because it appears bright at visible wavelengths.
Image 2: A perspective view looking at Doom Mons and Sotra Patera from the north-northeast This Cassini image is a combination of RADAR data (SAR images and a Digital Topographic Model or DTM produced from two SAR swaths) and VIMS data showing compositional differences in false color. The DEM data has a vertical exaggeration of 10:1. A movie showing the whole region can be seen at: http://photojournal.jpl.nasa.gov/catalog/PIA13695
One of the tallest peaks on Titan, Doom Mons, is ~70 km in diameter and 1.45 +/- 0.2 km high. It lies adjacent to the deepest depression so far found on Titan, Sotra Patera, which is an elongated pit ~30 km in diameter and 1.7 +/-0.2 km deep. These features, and the surrounding flow-like features around them (Mohini Fluctus), have been interpreted as cryovolcanic features(Lopes et al, 2013). Volcanism that occurs on the outer solar system’s satellites, sometimes known as cryovolcanism, includes the eruption of water-melts from the interiors of icy satellites onto their surfaces. (Kargel, 1995) (see also December 2008Image of the Month). In Image 2 Doom Mons and Sotra Patera are shown in a false colour composition map derived from VIMS data where shades of green and yellow indicate the candidate cryovolcanic materials and the dune fields are in shades of blue signifying a different composition.
The topography of cryo-volcanic features is of great importance for understanding the rheology and, by inference, the chemical composition, of cryomagmas on Titan. Therefore, accurate topographical measurements of cryo-volcanic regions will be a focus of future investigations. Cryo-volcanism may be an important resurfacing mechanism on Titan and present-day cryo-volcanic activity is feasible, though it has not been observed.
Image and caption contributed byProf. Dr. Ralf Jaumann, German Aerospace Center, Berlin, Germany andMary C. Bourke, Planetary Science Institute, Tucson, Az, 85719, USA.
The NASA Dawn spacecraft was launched in September 2007 to characterize the conditions and processes of the solar system's earliest epoch by investigating in detail two of the largest protoplanets remaining intact since their formation. Ceres and Vesta reside in the extensive zone between Mars and Jupiter together with many other smaller bodies, called the asteroid belt. Each has followed a very different evolutionary path constrained by the diversity of processes that operated during the first few million years of solar system evolution. The Dawn missionentered orbit around Vesta on 16 July 2011 for a one-year exploration and left orbit on 5 September 2012 heading towards Ceres.
Vesta is one of the brightest objects and it is also one of the largest asteroids in the Solar System with a mean diameter of 525 km. Impact-related processes have played a dominating role in (re-)shaping Vesta’s surface. Image A shows a colored perspective view of Vesta’s surface, taken by the Dawn framing camera. From top to bottom, the three most prominent craters were named Marcia, Calpurnia and Minucia and are 58 km, 50 km and 21.5 km in diameter, respectively. They are approximately oriented along a southwest-northeast direction. The three craters, initially nicknamed ‘the snowman crater’, represent a time sequence of impact events, with Minucia having firmed first and Marcia having formed last, and most likely with some time on the orders of thousands or even tens of thousands of years in between the impacts. However, all three craters are comparably young compared to the old, densely cratered surface of Vesta, as inferred from the low frequency of small craters superimposed on their floors and ejecta blankets. The ejecta materials of Marcia and Calpurnia cover entirely, or in some parts subdue, the older cratered plains. The ejecta superposes the northern terrains and covers underlying older terrains. Outside these ejecta Vesta’s heavily cratered northern terrain is apparent, especially in the right part of the image where crater rims are enhanced by shadows.
Vesta’s surface is characterized by abundant impact craters, some with preserved ejecta blankets, large troughs extending around the equatorial region, enigmatic dark material, and widespread mass wasting, but as yet an absence of volcanic features (Jaumann et al., 2012). Abundant steep slopes indicate that impact-generated surface regolith is underlain by bedrock.
Image and caption provided by Kelsi Singer. Ph.D Candidate, Earth and Planetary Sciences, Washington University, USA.
A typical landslide runs out less than two times its drop height whereas a long-runout landslide can extend 20-30 times the height it dropped from. Long-runout landslides (sturzstroms) are found across the Solar System. They have been observed primarily on Earth (Image 1) and Mars, but also on Venus, and Jupiter’s moons Io and Callisto.
Image 1: An example of a long-runout landslide on Earth is the Blackhawk landslide in the Lucerne Valley, California. This landslide travelled ~8 km. Image Source USGS
Glass-rich sand dunes and plains suggest Ice-magma interactions on Mars
IAG Planetary Geomorphology Working Group
Featured images for June 2012:
Glass-rich sand dunes and plains suggest Ice-magma interactions on Mars
Images and Caption contributed by Briony Horgan, Postdoctoral Fellow, School of Earth and Space Exploration, Arizona State University, USA
Several large, overlapping basins dominate the northern hemisphere of Mars, and are collectively termed the northern lowlands. This ancient basin has been infilled by sediments and hosts some of the darkest terrains on the planet. A new spectral investigation of these dark terrains has revealed that they are almost entirely composed of iron-bearing glass. This is the first detection of glass on Mars, as most other martian surfaces exhibit a typical basaltic composition with abundant olivine and pyroxene. In total, glass-rich materials cover nearly ten million square kilometers in the northern lowlands (Horgan and Bell, 2012).
Image 1 Caption: The prime meridian of Mars from Hubble. The large dark region in the northern hemisphere (Acidalia Planitia) is approximately 5 million square kilometers in area. The north polar cap and encircling north polar sand sea can also be seen at the top of the image (NASA/Lee/Bell/Wolff)
Surface dissolution on Titan and Earth: Ontario Lacus and the Etosha Pan (Namibia) .
IAG Planetary Geomorphology Working Group
Featured images for May 2012:
Surface dissolution on Titan and Earth: Ontario Lacus and the Etosha Pan (Namibia) .
Image and caption contributed by Thomas Cornet, Olivier Bourgeois, S. Le Mouélic et al.. Laboratoire de Planétologie et Géodynamique de Nantes, UMR 6112, CNRS, Nantes, France.
Titan, Saturn’s major moon, possesses hydrocarbon lakes and seas in the polar regions [Stofan et al., 2007, Hayes et al., 2008]. Among these, Ontario Lacus (72°S, 180°E, Image 1) is the largest in the south (235 km-long, 75 km-wide). So far it is interpreted as a liquid-covered lake in Titan’s southern hemisphere because of its dark appearance in Cassini image data [Barnes et al., 2009; Turtle et al., 2009; Hayes et al., 2010; Wall et al. 2010], the identification of liquid ethane in its interior [Brown et al., 2008] and the smoothness of its surface [Wye et al., 2009].
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