Curiosity Blog, Sols 4995-5001: 5,000 (Martian) Days on Mars

Written by William Farrand, Senior Research Scientist, Space Science Institute

Earth planning date: Friday, Aug. 28, 2026

The span of sols spanned by this blog post is noteworthy in several ways. First, Curiosity became a world-class (for Mars at least) mountaineer by passing the 1 kilometer mark of elevation from its landing site on the floor of Gale crater. This writer was on the Mars Exploration Rover science team and we were excited when the Spirit rover got to the top of Husband Hill in Gusev crater in August 2005. But that was a climb of 106 meters (about 348 feet) above its landing site, and Curiosity has passed 1000 meters (about 0.62 miles). 

Second, Saturday, Aug. 29, marked 5,000 Martian days (or sols) since Curiosity landed on Mars (that's more than 5,137 Earth days, because a day on Mars lasts 24.6 hours). Congratulations are in order to the engineers and scientists who have made this landmark possible. 

Finally, in terms of its science activities Curiosity is examining a wind-formed, long, narrow, large ripple which has been named “Chocolatal.” Further examination will help determine if this feature could be classified as a “transverse aeolian ridge” or TAR. TARs have been observed across the Martian surface based on orbital imaging. The long axis of a TAR is oriented perpendicular to the local predominant wind direction. While this is not the first potential TAR that has been examined by Curiosity, its location, higher on the slopes of Mount Sharp invites questions about whether it will be composed of the same types of granular materials found in the lower TARs, or whether it has a different range of grain sizes and/or layering. 

Other questions to be addressed include how the ridge formed, whether it is active, how it has migrated, and, if it is immobile, then how has it stabilized?

At the start of the planning week, Curiosity was en route to the sand ripple and encountered interesting science targets along the way. In Monday’s two-sol plan, in-situ examinations were planned of the light-toned bedrock occurring along the rover’s path. Some of the rocks encountered near the rover had dark-toned thick coatings or remnant layers, and these were targeted for chemical examination by the rover’s ChemCam Laser Induced Breakdown Spectroscopy (LIBS) instrument. Mastcam and ChemCam Remote Micro Imager (RMI) mosaics were planned, for layers in buttes along the rover’s path, and on more distant sets of sand ripples.

A midweek planning session took advantage of the last drive, leaving the rover only a few meters from Chocolatal. ChemCam was able to target sand at the base of Chocolatal as well as nearby bedrock. Stand-off Mastcam high-resolution image mosaics of the ripple were also targeted. The drive planned midweek took the rover right into Chocolatal with one of its wheels and then backing off a little, so in the end-of-week plan, contact science could be planned within the trenched region.

The final planning session of the week, which extended through the landmark Sol 5000, involved MAHLI mosaics of the right wall of the trench to see if there is layering, and to assess any variations in grain size. It’s noteworthy that these MAHLI mosaics are being named in honor of our late colleague Paul Geissler, who was one of the foremost experts on the study of Martian TARs and who was working with the MAHLI team before his untimely passing earlier in the year. In-situ APXS measurements were planned of the coarse-grained surface of the ripple, and ChemCam LIBS measurements were planned on the top of Chocolatal, a sinuous feature looking like a “mohawk” haircut (see the accompanying image). LIBS was also planned on a dark band on its flank and at the back of the scuff/trench. Other activities in the three-sol plan included Mastcam mosaics, an AM Navcam dust-devil survey, Navcam suprahorizon survey, and APXS atmospheric measurements.

With 5000 sols of outstanding scientific accomplishments, the Curiosity science and engineering team looks forward to the next 5000 sols.