Holden Delta Layers
Highlighted Portion of HiRISE Image TRA_000861_1530This HiRISE image covers a portion of the floor of Holden Crater situated in southwest Margaritifer Terra. Holden crater has likely experienced extensive modification by running water, which is supported by observations of drainage and deposition into the crater from a large channel breaching Holden's rim and the alluvial fans that built out along the floor of the crater. The HiRISE sub-image shows relatively bright finely layered deposits that are capped by relatively darker materials. Unlike previous images, the HiRISE image shows that the thickness of some of the individual layers are on the order of a meter or even less in thickness and are laterally uniform and continuous over the extent of the imaged outcrop. Some of the layers in the outcrop display an orthogonal pattern or what may be fractures or joints. The "layer-cake" appearance of these layers suggests that they may have been deposited into a lake that once occupied the crater floor and have seen little in the way of deformation since that time. By contrast, the darker materials overlying the layers are younger and may have been sediments deposited off the nearby alluvial fans. Alternatively, they may represent wind-blown deposits lain down during a later much drier period similar to the conditions that currently exist at the surface today. In some locations, the darker materials have been stripped and expose the lighter finely layered sediments underneath, thereby implying the finely layered materials extend much farther than what is visible along the large outcrop.
Image TRA_000861_1530 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on October 2, 2006. The complete image is centered at -26.7 degrees latitude, 325.2 degrees East longitude. The range to the target site was 258.2 km (161.4 miles). At this distance the image scale is 51.7 cm/pixel (with 2 x 2 binning) so objects ~155 cm across are resolved. The image shown here [below] has been map-projected to 50 cm/pixel and north is up. The image was taken at a local Mars time of 3:33 PM and the scene is illuminated from the west with a solar incidence angle of 71 degrees, thus the sun was about 19 degrees above the horizon. At a solar longitude of 114.9 degrees, the season on Mars is Northern Summer.
HiRISE Image TRA_000861_1530
Images from the High Resolution Imaging Science Experiment and additional information about the Mars Reconnaissance Orbiter are available online at:
http://hirise.lpl.arizona.edu/
or
For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.
