The first Martian marathon was no easy trek: the Opportunity rover had to struggle through smooth, soft sand and clamber over sharp rocks. This is the sounds of the terrain it covered in its 11-year journey exploring the red planet.

In July 2014, the Mars Opportunity rover broke the off-world driving marathon. In March 2015, it completed the first extraterrestrial marathon. It wasn’t an easy marathon: this was an off-track, all-terrain monster of a race. This is the view from the rover’s hazard-avoidance camera [left frame] and a map tracking progress [right frame] set to a soundtrack where the auditory intensity reflects the roughness of the terrain, condensing 11 years into under 8 minutes.

The video is a compilation of images from NASA’s Mars Exploration Rover Opportunity as it journeyed over 42.2 kilometers (26.2 miles) from its landing location in January 2004 to Marathon Valley in April 2015. The rover has been studying the rim of the 22 kilometer (14 mile) diameter Endeavour Crater since 2011. Almost all the tracks from its journey are now gone, blown away by the frequent dust storms of Mars.

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The soundtrack reflects the roughness of the terrain, recorded as vibration measurements. When Opportunity rolled over soft, squishy sands, the soundtrack mellows into a quiet hiss (especially when the poor rover was stuck in a sand dune in May 2005); when it hauled its 185 kilogram mass over rough rocks, the soundtrack climbs to an angry growl.

Traces of Opportunity’s landing rocket blasts and earliest rover tracks were already fading between April 2004 [top] and November 2006 [bottom]. Image credit: NASA/JPL/Malin Space Science Systems/University of Arizona/JGR

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After the epic trek, Opportunity took a three-week break of reduced activity as the Martian solar conjunction interrupted communication. Since the rover no longer has the capacity to store data and needs to call home every night with a data downlink, it would’ve been futile for it to blast ahead with full sciencing when it couldn’t report back to Earth. Now it will bask on the sun-facing slopes of Marathon Valley, poking at clay-rich outcrops.

Opportunity completed its first Martian marathon in March 2015, immediately beginning its second by venturing into Marathon Valley. Image credit: NASA/JPL-Caltech/Univ. of Arizona

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Opportunity didn’t always rely exclusively on short-term memory. The non-volatile flash memory used to store data during overnight power-downs, but started glitching out. It was temporarily restored by reformatting, but started dying again this spring. Instead of arguing with the aging rover that robots aren’t supposed to develop amnesia, mission control switched to using random-access memory only, which can only retain data when the power is on, and downloading everything daily. As Opportunity Project Manager John Callas explains:

Opportunity can continue to accomplish science goals in this mod. Each day we transmit data that we collect that day. Flash memory is a convenience but not a necessity for the rover. It’s like a refrigerator that way. Without it, you couldn’t save any leftovers. Any food you prepare that day you would have to either eat or throw out. Without using flash memory, Opportunity needs to send home the high-priority data the same day it collects it, and lose any lower-priority data that can’t fit into the transmission.

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The durable Mars Opportunity rover basking in sunset on the rim of Endeavour Crater in 2012. Image credit: NASA/JPL-Caltech/Cornell/Arizona State Univ.

The Opportunity rover is working on its second marathon eleven years into its 90-day mission. Its twin Spirit worked for six years before declaring it had enough poking about for evidence of ancient wet environments.

Top image: Opportunity looking back towards the west rim of Endeavour Crater in August 2014. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

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