Investigating Mars: Ius Chasma

Moving into the central part of Ius Chasma, the canyon profile changes. What started as a large graben south of the main chasma wall, has widened to create a central high ridge separating the chasm into two parallel sections. This interior ridge is called Geryon Montes. The northern canyon wall is at the top of the image, including several tongue shaped landslide deposits. The floor has been covered in deposits that may include landslide material and later materials such as air fall particles like dust and water lain layered deposits. The Geryon Montes are in the lower 1/3 of the image. Just to the top of the Montes are materials with different "colors". These are part of the layered materials inside the canyon. At the very bottom of the image a highly eroded landslide deposit exists. The materials on this side of Geryon Montes are at a higher elevation than the floor on the opposite side. The unusual texture of the canyon floor also points to layered materials that may have been laid down in standing water.

A landslide is a failure of slope due to gravity. They initiate due to several reasons. A lower layer of poorly cemented/resistant material may have been eroded, undermining the wall above which then collapses; earthquake seismic waves can cause the slope to collapse; and even an impact event near the canyon wall can cause collapse. As millions of tons of material fall and slide down slope a scalloped cavity forms at the upper part where the slope failure occurred. At the material speeds downhill it will pick up more of the underlying slope, increasing the volume of material entrained into the landslide. Whereas some landslides spread across the canyon floor forming lobate deposits, very large volume slope failures will completely fill the canyon floor in a large complex region of chaotic blocks.

Ius Chasma is at the western end of Valles Marineris, south of Tithonium Chasma. Valles Marineris is over 4000 kilometers long, wider than the United States. Ius Chasma is almost 850 kilometers long (528 miles), 120 kilometers wide and over 8 kilometers deep. In comparison, the Grand Canyon in Arizona is about 175 kilometers long, 30 kilometers wide, and only 2 kilometers deep. The canyons of Valles Marineris were formed by extensive fracturing and pulling apart of the crust during the uplift of the vast Tharsis plateau. Landslides have enlarged the canyon walls and created deposits on the canyon floor. Weathering of the surface and influx of dust and sand have modified the canyon floor, both creating and modifying layered materials. There are many features that indicate flowing and standing water played a part in the chasma formation.

The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 71,000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside craters and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images!