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

The scene combines views from the left eye and right eye of Opportunity's panoramic camera (Pancam) to appear three dimensional when seen through blue-red glasses with the red lens on the left. It is a mosaic of Pancam frames taken 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.

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.

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.

An approximately true color version of the Knudsen Ridge scene is at PIA20318. An enhanced color version is at PIA20319.

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