Terra Sirenum Gullied Crater
This color image covers only the center swath of
the full image, and is composed of images acquired through red and
blue-green filters. The color has been enhanced to better show the subtle
color differences. It is not natural color or how it would appear to
normal human vision.
This enhanced color sub-image shows gullies in an unnamed crater in the Terra Sirenum region of Mars. The scene is ~254m (~830ft) wide. The upper and left regions of this scene are in shadow, yet color variations are still apparent. The high signal to noise ratio of the HiRISE camera allows for colors to be distinguished in shadows. This allows dark features to be identified as true albedo features vs. topographical features.
This region receives very little sunlight in the current season (southern winter), and the bluish areas consist of frost. At the latitude of this image, frost is most likely composed of water because the temperature is not low enough for carbon dioxide condensation. The reddish regions are locations where frost has been removed, most likely by sublimation. The dark, unfrosted regions (for example, in the channel of the gully on the far right) represent the most recent activity in the gullies and are possibly a result of seasonal melting.
Besides acquiring monochromatic images of 6km swath width and variable length, HiRISE can also image the central 20% of the swath width in color. Color images can help resolve ambiguities in image interpretation, and will enable us to place compositional data from other experiments into more specific geologic context. HiRISE can "see" color in the visible range (the red, green, and blue portions of the spectrum) and beyond (in the near infrared), thus allowing for the detection of—among others—characteristic alteration minerals which require water to form.
Image TRA_000878_1410 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on Sunday, 04 October 2006. The complete image is centered at -38.9 degrees latitude, 223.7 degrees East longitude. The range to the target site was 251.8 km (157.4 miles). At this distance the image scale is 50.4 cm/pixel (with 2 x 2 binning) so objects ~151 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 3:38 PM and the scene is illuminated from the west with a solar incidence angle of 80 degrees, thus the sun was about 10 degrees above the horizon. At a solar longitude of 115.5 degrees, the season on Mars is Northern Summer.
Images from the High Resolution Imaging Science Experiment and additional information about the Mars Reconnaissance Orbiter are available online at:
http://www.nasa.gov/mro
or
http://HiRISE.lpl.arizona.edu.
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.
