Posted by Dr P. Senthil Kumar, National Geophysical Research Institute, Council of Scientific & Industrial Research, Hyderabad 500007, India.
Gullies are well-known geomorphic features on Earth where they are mainly formed by erosion due to flow of liquid water. They are also detected on Mars and the Moon and their origin on those bodies are under discussion (Malin and Edgett, 2000; Senthil Kumar et al., 2010). The gullies consist of alcoves (erosional features), channels (features indicating transportation) and fans or debris aprons (depositional structures). These features are clearly observed on the interior walls of impact craters on Mars and widely on the mountain slopes of Earth. Hence, geomorphologists use these features to examine the characteristics of liquid water flow either in the present or past geological records.
Image 1: (a) The Chandrayaan-1 terrain mapping camera image showing the ~7.2-km-diameter fresh crater (centred at 72º12’S, 133º12’E) emplaced in the peak-ring material of Schrödinger basin. The topographic profiles along A-A’ and B-B’ are shown in Figure 1d. A 6860-m-diameter circle fits perfectly to the crater rim from the western to the northern sides of the crater, while the crater rim recedes in other parts due to enhanced crater wall erosion. (b) The shadow-enhanced TMC image reveals the presence of arcuate ridge and the pond material on the crater floor. Note the pond is oriented toward the prominent landslide surface. (c) The TMC image showing the presence of concentric faults along the northwestern crater rim. (d) The topographic profiles along A-A’ and B-B’. The interior wall that contains the landslides (B-B’) is gentler and shallower than the interior wall with the gullies (A-A’). The ridge material is characterized by a higher topographic relief than the surrounding crater floor. The pond material has a flat surface that embays the ridge and other floor materials. See Senthil Kumar et al. (2013) for more details.
Posted by megafloods2013 on December 1, 2013
Posted by Rebecca Thomas, Department of Physical Sciences, The Open University, UK.
Recent channelized flows from vents in the Cerberus plains of Mars demonstrate the difficulties of uniquely ascribing process to landforms on other planets. The image below shows two fissures emanating from a wrinkle ridge. Both fissures appear to be sources of approximately contemporaneous channels running down onto the surrounding plains (Thomas, 2013). The channel in the west is constructive and differs from that in the east which is clearly shows several phases of incision (Image 1).
Image 1: a. Vents and channels in the Cerberus plains, Mars (156.9° E, 7.1° N); b. incised channel; c. constructed, leveed channel. (HiRISE ESP_016361_1870)
Posted by megafloods2013 on November 4, 2013
Post by Scott Mest, Planetary Science Institute, Tucson, AZ 85719, USA.
Lunar sinuous rilles (German for ‘groove’) consist of long, narrow depressions in the lunar surface that meander in a curved path across the surface and morphologically resemble terrestrial fluvial channels (Image 1). Sinuous rilles are generally up to several kilometers wide and hundreds of kilometers in length. On the Moon, sinuous rilles are found within volcanic terrains such as the extensive lunar mare. Their morphology and association with volcanic deposits suggests that they are the remains of lava channels or collapsed lava tubes.
Image 1: Part of LROC image M115429448L (resolution is 0.970 m/pixel) showing a close-up of a sinuous rille (arrows) that cuts through dark plains (p) and adjacent hilly (h) materials on the floor of Schrödinger.
Posted by megafloods2013 on September 16, 2013