NASA's Curiosity rover has now spent 5,000 Martian days on the Red Planet, a milestone the mission team marked in a Curiosity mission blog post published Sept. 9. Sol 5,000 fell on Saturday, Aug. 29, according to the post, which was written by William Farrand, a senior research scientist at the Space Science Institute.

A Martian day, or sol, lasts about 24.6 hours, so the rover's 5,000 sols add up to more than 5,137 Earth days, or a little over 14 years. Curiosity was designed for a prime mission of one Martian year. It completed that first year, equal to 687 Earth days, in June 2014, according to a NASA update marking the rover's first Martian year. It has now operated for about seven and a half Martian years.

The milestone matters because every extra year has let the rover keep climbing Mount Sharp, a 3-mile-tall (5-kilometer) mountain of sedimentary rock whose layers record how Mars changed from a world with lakes and streams to a drier planet. Curiosity is still reading that record with instruments built before its 2011 launch.

Fourteen Years, 5,000 Sols and One Kilometer Up

Curiosity launched Nov. 26, 2011, and landed in Gale Crater on Aug. 6, 2012, according to NASA's mission page. In California, where the mission is run, it was still the evening of Aug. 5. The rover has been climbing Mount Sharp since 2014.

On Aug. 26, the rover marked an elevation gain of 1 kilometer, or about 0.62 miles, above its landing site on the crater floor, NASA reported. Farrand put that in perspective by recalling the Spirit rover's climb to the top of Husband Hill in Gusev Crater in 2005, which gained 106 meters (about 348 feet). He wrote that the climb had made Curiosity "a world-class (for Mars at least) mountaineer."

The rover is not coasting through the milestone. During the week that included sol 5,000, the team drove one of its wheels into a long, narrow, wind-formed ripple nicknamed Chocolatal, then backed off to leave a small trench. The plan for the end of that week called for close-up imaging of the trench wall to look for layering and changes in grain size, along with chemical measurements of the ripple.

Scientists want to know whether the feature is a transverse aeolian ridge, a type of wind-formed ridge seen from orbit across Mars. They also want to learn whether this one, sitting higher on Mount Sharp, is made of different grains than similar ridges lower down. The team is naming its close-up image mosaics of the trench in honor of Paul Geissler, a colleague and leading expert on these ridges who died earlier this year, according to the blog.

Reading a Planet's Climate Shift in Rock

Mount Sharp is built in layers, with older rock at the bottom and younger rock above. As Curiosity climbs, it effectively moves forward in Martian time.

The first major payoff came early. Within its first Martian year, the rover drilled into an ancient lakebed near its landing site and found the ingredients and conditions that could have supported microbial life, meeting the mission's main goal before it reached the mountain.

The extended years have been spent tracing what happened next. Lower on the mountain, the rover crossed thick deposits laid down in lakes. Higher up, it passed through a clay-rich region and a transition zone into a sulfate-bearing unit, where salty minerals are thought to have been left behind as water dried to a trickle.

"Instead, we see lots of evidence of drier climates," project scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory said in a 2022 NASA release, after noting that the team no longer saw the lake deposits found lower on the mountain. He described dry dunes that occasionally had streams running around them, a big change from lakes that may have persisted for millions of years.

The picture is not a simple slide into drought. A 2021 study in the journal Geology led by William Rapin, based on long-distance observations by the rover, described lake mudstones giving way to dunes, then water-laid rock. The authors concluded that the record implies multiple swings between sustained drier and wetter climates rather than one steady march toward aridity. In 2023, NASA also reported that Curiosity had found rippled rock textures, its clearest evidence of waves in ancient lakes, inside the sulfate-bearing unit, a region scientists had expected to be drier.

Curiosity's long run has also produced chemistry results that take years to finish. NASA's mission page highlights a Feb. 4 study in the journal Astrobiology that examined the largest organic compounds yet found on Mars, detected in a drilled mudstone sample called Cumberland. The researchers said the non-biological sources they considered could not fully account for the amount of those compounds, which have been hypothesized to be fragments of fatty acids. That is not evidence of life, and the origin of the molecules remains an open question.

Wheels Worn by Years of Sharp Rock

The climb has come at a cost to hardware. Engineers first observed an alarming rate of cracking in the rover's wheel skins about 14 months after landing, according to a JPL engineering assessment of the wheel damage. As of Aug. 2, 2021, four of the raised treads, called grousers, had broken: three on the left middle wheel and one on the right middle wheel.

The assessment found that the damage did not significantly limit mission objectives at the time, but it said a higher damage rate could affect surface operations, so the rate is closely monitored. The operations team has imaged the wheels periodically since Nov. 30, 2013, and those assessments have shaped the rover's driving guidelines.

Routine imaging is also yielding new science. In April, NASA released a six-year time-lapse from a navigation camera spanning Jan. 2, 2020, to March 8, 2026. The team is using the sequence to watch sand grains shift on the rover's deck, which can help separate jolts from driving from wind gusts and reveal seasonal changes in the atmosphere.

Limits of the Record and the Climb Ahead

Several questions remain open. Results from the Chocolatal measurements have not been published, so it is not yet known whether the ridge is active, how it formed or how it compares with ridges lower on the mountain. The organic-molecule findings describe chemistry, not biology. The milestone post does not assess the condition of the wheels or other systems, and the wheel assessment cited here reflects conditions as of 2021.

A rover designed for a mission of about two Earth years is now 14 years into its work, 1 kilometer up a Martian mountain and still returning clues to how a once-wetter planet dried out. The team closed its milestone post by saying it looks forward to the next 5,000 sols.

The next results to watch for are the team's findings on the Chocolatal ridge and any update on wheel condition. Readers can follow along through the mission's regular team updates and the raw images NASA posts publicly.

What Readers Want to Know

How long is 5,000 sols in Earth time?

A sol, or Martian day, lasts about 24.6 hours. That makes 5,000 sols equal to more than 5,137 Earth days, or a little over 14 years. Curiosity reached sol 5,000 on Aug. 29, 2026.

How long was Curiosity supposed to last?

Its prime mission was one Martian year, which is 687 Earth days, or just under two Earth years. The rover has now operated for about seven and a half Martian years.

Why do scientists care so much about Mount Sharp?

The mountain is built from stacked sedimentary layers, with the oldest at the bottom. Climbing it lets the rover read how Mars changed from a world with lakes and streams to a drier planet, including evidence that the shift happened in swings rather than one steady trend.

Are Curiosity's wheels about to fail?

NASA has not said so. A JPL assessment found that wheel damage, first noticed about 14 months after landing, did not significantly limit the mission as of 2021. The team monitors the damage rate and has adjusted its driving guidelines.

Did Curiosity find signs of life?

No. The rover found evidence that ancient Gale Crater had conditions that could have supported microbes, and it has detected large organic molecules. Organic molecules can form without life, and their origin on Mars remains unresolved.

What was Curiosity studying at the 5,000-sol mark?

The team was examining a wind-formed ripple nicknamed Chocolatal to learn whether it is a transverse aeolian ridge, how it formed, whether it is still active and how its grains compare with ridges lower on the mountain.