This scene from NASA's Mars Exploration Rover Opportunity looks upward at 'Knudsen Ridge' on the southern edge of 'Marathon Valley' from inside the valley.

This scene from NASA's Mars Exploration Rover Opportunity looks upward at "Knudsen Ridge" on the southern edge of "Marathon Valley" from inside the valley.

The view combines multiple images taken with the panoramic camera (Pancam) on Opportunity's mast on Oct. 29 and Oct. 30, 2015, during the 4,182nd and 4,183rd Martian days, or sols, of the rover's work on Mars. By February 2016, the rover ascended slopes of about 30 degrees onto the flank of Knudsen Ridge, headed for targets of "red zone" material to examine there.

This version of the scene is presented in approximately true color. An enhanced-color version, which makes the red zone material easier to distinguish, is at PIA20319. A stereo version is at PIA20320.

The informal name Knudsen Ridge was chosen by the Opportunity science team to honor the memory of Danish astrophysicist and planetary scientist Jens Martin Knudsen (1930-2005), a founding member of the team.

Color in the scene comes from component images taken through three of the Pancam's color filters, centered on wavelengths of 753 nanometers (near-infrared), 535 nanometers (green) and 432 nanometers (violet). The view spans from southeast on the left to southwest on the right.

Marathon Valley cuts generally east-west through the western rim of Endeavour Crater. The valley's name refers to the distance Opportunity drove from its 2004 landing site to arrival at this location in 2014. The valley was a high-priority destination for the rover mission because observations from orbit detected clay minerals there.

For more about Opportunity's mission, see http://mars.nasa.gov/mer.

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