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“Marathon Valley” on Mars opens northeastward to a view across the floor of Endeavour Crater in this scene from the panoramic camera (Pancam) of NASA’s Mars Exploration Rover Opportunity.
The scene merges multiple Pancam exposures taken during the period April 16 through May 15, 2016, corresponding to sols (Martian days) 4,347 through 4,375 of Opportunity’s work on Mars. It spans from north, at the left, to west-southwest, at the right.
The high point in the right half of the scene is “Knudsen Ridge,” which forms part of the southern edge of Marathon Valley. Portions of the northeastern and eastern rim of Endeavour crater appear on the distant horizon. Endeavour Crater is 14 miles (22 kilometers) in diameter. The fractured texture of Marathon Valley’s floor is visible in the foreground.
The view merges exposures taken through three of the Pancam’s color filters, centered on wavelengths of 753 nanometers (near-infrared), 535 nanometers (green) and 432 nanometers (violet). It is presented in approximately true color.
The rover team calls this image the mission’s “Sacagawea Panorama,” for the Lemhi Shoshone woman, also commemorated on U.S. dollar coins, whose assistance to the Lewis and Clark expedition helped enable its successes in 1804-1806. Many rocks and other features in Marathon Valley were informally named for members of Lewis and Clark’s “Corps of Discovery” expedition.
Opportunity entered Marathon Valley in July 2015. The valley’s informal name was chosen because Opportunity’s arrival at this point along the western rim of Endeavour Crater coincided closely with the rover surpassing marathon-footrace distance in its total driving odometry since landing on Mars in January 2004. The team’s planned investigations in the valley were nearing completion when the component images for this scene were taken.
Rover Opportunity Wrapping up Study of Martian Valley
“Marathon Valley,” slicing through a large crater’s rim on Mars, has provided fruitful research targets for NASA’s Opportunity rover since July 2015, but the rover may soon move on.
Opportunity recently collected a sweeping panorama from near the western end of this east-west valley. The vista shows an area where the mission investigated evidence about how water altered the ancient rocks and, beyond that, the wide floor of Endeavour Crater and the crater’s eastern rim about 14 miles (22 kilometers) away.
Marathon Valley lured the mission because researchers using NASA’s Mars Reconnaissance Orbiter had mapped water-related clay minerals at this area of the western rim of Endeavour Crater. The rover team chose the valley’s informal name because Opportunity’s arrival at this part of the rim coincided closely with the rover surpassing marathon-footrace distance in total driving since its January 2004 Mars landing.
“We are wrapping up our last few activities in Marathon Valley and before long we’ll drive away, exiting along the southern wall of the valley and heading southeast,” said Opportunity Principal Investigator Steve Squyres, of Cornell University, Ithaca, New York.
As Opportunity examined the clay-bearing rocks on the valley floor that were detected from orbit, the rover’s own observations of the valley’s southern flank revealed streaks of red-toned, crumbly material. The science team chose to investigate this apparently weathered material. The rover approached exposures of it to prepare for using the Rock Abrasion Tool, called the RAT. This tool grinds away a rock’s surface to expose the interior for inspection.
“What we usually do to investigate material that’s captured our interest is find a bedrock exposure of it and use the RAT,” Squyres said. “What we didn’t realize until we took a close-enough look is that this stuff has been so pervasively altered, it’s not bedrock. There’s no solid bedrock you could grind with the RAT.”
Instead, the rover exposed some fresh surfaces for inspection by scuffing some of the reddish material with a wheel.
Squyres said, “In the scuff, we found one of the highest sulfur contents that’s been seen anywhere on Mars. There’s strong evidence that, among other things, these altered zones have a lot of magnesium sulfate. We don’t think these altered zones are where the clay is, but magnesium sulfate is something you would expect to find precipitating from water.
“Fractures running through the bedrock, forming conduits through which water could flow and transport soluble materials, could alter the rock and create the pattern of red zones that we see.”
As of June 14, Opportunity has driven 26.59 miles (42.79 kilometers). NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, built the rover and manages the mission for NASA’s Science Mission Directorate, Washington.
source : NASA – Jet Propulsion Laboratory – California Institute of Technology