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.
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.
Posted by suja82 on October 28, 2016
Posted by Mary Bourke, Geography, Trinity College, Dublin, Ireland.
(Re-posted from IAG Image of the Month, June, 2007)
Both Earth and Mars have atmospheres that can mobilize particles to form sand dunes. This image is from the caldera of an inactive Volcano (Nili Patera) on Mars. The steep avalanche face on the downwind side of the dunes indicates wind direction (see arrow). There are several types of sand dunes in this image, some of which have not been previously recognized on Mars. (more…)
Posted by megafloods2013 on July 2, 2013