The main purpose of my work is to create a geomorphologic map of the western part of Valles Marineris (Fig. 7). In addition, I am preparing a synthesis of the geological history of the entire trough complex on the basis of previous studies and my current findings.

Fig. 7 Geomorphological map of Ius Chasma (status in January 2015)

Valles Marineris extends over 650 km x 2000 km in the equatorial part of Mars. Internal trough landforms inform on 4 Gy of Mars’ history, recording a broad range of magmatic, tectonic, fluvial, lacustrine, glacial, eolian, and gravitational processes. The investigated area includes Ius, Tithonium and western Melas chasmata, where trough contours, landslide scarps and main geomorphological bodies, ILDs, dune areas, sapping channels, spur and gullies, floor features, and different wall types are mapped.

The background mosaic was created on the basis of 100 Context Camera (CTX) images obtained by the Mars Reconnaissance Orbiter (MRO). The image processing has been fulfilled using the ISIS Planetary Image Processing Software, including five sub-programmes: mroctx2isis, spiceinit, ctxcal, ctxevenodd, cam2map and isis2std. The images have become georeferenced, radiometrically calibrated, devoid of dead pixels, and projected. During these changes the image resolution was decreased from 6 to 12 m/pixel. In order to enable ISIS software to match file size limitations for the mosacing process (indicated in brackets), the image collection was divided into three smaller sets (western, central and eastern). Each set was adjusted by tone matching equalizer and mosaic creating automos (12 GB), and eventually converted to PNG file in isis2std (2 GB). Additionally, MRO HiRISE images, Mars Global Surveyor (MGS) MOLA altimeter datasets and MGS Mars Orbiter Camera (MOC) images were also used for interpretation.

During the past year, I have mapped a number of geologic and geomorphologic features, i.e. dune areas (Ʃ >10 000), craters (Ʃ >5000), sapping channels (rocky wall top, main slope, floor), pit chains, walls of spur-and-gully morphology, large landslide scarps, collapsed rocks of landslides (8 types), lonely buttes, small landslides, collapsed walls, boulders, lobate landforms, tongue-shaped landform, valley infill, spur crests on walls (Ʃ 12 439 km), chasma contours (Ʃ 8866 km), periglacial floor landforms, evaporate-like floor areas, and other floor features.

Dune areas cover a significant part of chasma floor, but they are not a homogeneous unit. Valles Marineris dunes are characterized by different: type (barchans, transverse dunes, longitudinal dunes), lithology (bright and dark dunes), exposure size of single dune area (from ~100 m² to ~100 km²), and sand source. Among 20 largest dune fields on the Ius Chasma floor, the average dune spacing (measured between crests) is 50 m and the predominant facing direction of dune slopes is W-E. These transverse and longitudinal dunes are built of sand from intra-chasma main sources (landslides, walls) and secondary sources (interior layered deposits (ILDs), floors and craters). Dunes originated in landslides dominate in the northern trough, whereas wall-related dunes are widespread in the entire chasma. Floor source is a stratigraphically homogeneous unit observed in the southern Ius trough, probably of detrital origin, in which dunes occupy erosional hollows. Crater dune fields are rare.

Analysis of spur and gully morphology has revealed three chasma wall types: active (with a visible evidence of modern sediment transport; common), inactive (with a lack of transport; rare) and grooved (displaying up to 100-meter wide shallow flat-floored linear grooves parallel or oblique to the local slope; common on the central Ius inner ridge). The grooves might result from a creeping process of viscous surface material.

Glacial and periglacial landforms were determined in the western part of Ius Chasma. The area consists of three regions: moraine area, till plain, and outwash plain, localized in accordance with the floor inclination.

Sapping channel systems are present mostly in the southern part of Ius Chasma. They are characterized by different length (14-150 km), area (47-2270 km²), sinuosity (1,0-1,2), number of branches (1-20), and maturity (number of collapsed walls inside). In one system, tongue-shaped flowing feature (probably periglacial) was determined.

Systematic high-resolution mapping in Valles Marineris is revealing geomorphologic features and processes that had not been recognized before. I will present full mapping results in June 2015.