Check it out — a boulder track on Mars. No speculation on what dislodged the boulder. Perhaps a close meteor strike making one of the larger craters shook it loose or it could even be ejecta from an impact like some of the ones we see on our moon. If you follow the track to the origin there almost looks like a small pit at the beginning.
We are seeing this track thanks to the HiRISE image on board the Mars Reconnaissance Orbiter.
A path resembling a dotted line from the upper left to middle right of this image is the track left by an irregularly shaped, oblong boulder as it tumbled down a slope on Mars before coming to rest in an upright attitude at the downhill end of the track. The High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter recorded this view on July 14, 2014.
The boulder’s trail down the slope is about one-third of a mile (about 500 meters) long. The trail has an odd repeating pattern, suggesting the boulder could not roll straight due to its shape.
Calculated from the length of the shadow cast by the rock and the known angle of sunlight during this afternoon exposure, the height of the boulder is about 20 feet (6 meters). Its width as seen from overhead is only about 11.5 feet (3.5 meters), so it indeed has an irregular shape. It came to rest with its long axis pointed up.