After 11 years on Mars, Curiosity continues to climb the slopes of Mount Sharp

by Haygen Warren

On Aug. 6, 2012, NASA’s Mars Science Laboratory mission, comprised of the new Curiosity rover, officially began when Curiosity was successfully lowered onto the Martian surface via a first-of-its-kind skycrane. Curiosity‘s landing location was at the base of Mount Sharp (officially referred to as Aeolis Mons) in Gale Crater — a 3.5 billion-year-old crater that scientists believe was once a lake.

In the 11 years since its historic landing, Curiosity has explored Gale Crater extensively, collecting data on Martian soil, rock formations, weather, and more. In September 2014, after exploring its landing region, named Aeolis Palus, and completing an eight-kilometer trek to the base of Mount Sharp, Curiosity began climbing up the slopes of Mount Sharp. Every day since then, the rover has continued to slowly creep toward the top of Mount Sharp and has made scientific discoveries that will change planetary science and astrobiology forever.

Curiosity and its team will celebrate its 11th anniversary by doing what the rover does best: exploring Mars. Throughout the last several weeks, Curiosity explored a region of Mount Sharp called “Jau.” The region is covered with dozens and dozens of small impact craters that Curiosity and its team had to carefully navigate.

The number of craters within Jau made the region an area of interest for Curiosity scientists. Planetary scientists rarely get the opportunity to view so many craters up-close and are eager to learn more about what the region was like when liquid water freely flowed on Mars. As mentioned, Gale Crater was once thought to be a lake, and given that Mount Sharp sits at the center of the crater, scientists also believe that the five-kilometer-tall Mount Sharp was covered with hundreds of rivers, streams, ponds, and more.

Curiosity’s view of Mount Sharp on Sept. 20, 2012. (Credit: NASA/JPL-Caltech/MSSS)

While scientists were eager to explore and learn more about Jau and its links to ancient Mars, Jau was just a pit-stop for the rover as it continued to make its way up Mount Sharp. Curiosity‘s climb up Mount Sharp is extremely impressive given the rover’s age and condition, but it certainly hasn’t been without its challenges.

The route Curiosity has been following up Mount Sharp over the last few months has been the most difficult climb the rover has faced yet. As Curiosity continues to climb higher and higher up the mountain, slopes begin to get steeper and the Martian terrain becomes more jagged and dangerous. Due to this, Curiosity and its team have had to be extra careful with the routes they take. Throughout May and June, Curiosity climbed a slope that featured a 23-degree incline, slippery sand, and rocks the size of Curiosity‘s wheels.

While the climb up Mount Sharp has certainly been difficult for Curiosity, the climb has also brought with it a great deal of stress for the scientists that operate Curiosity back on Earth.

“If you’ve ever tried running up a sand dune on a beach – and that’s essentially what we were doing – you know it’s hard, but there were boulders in there as well,” said Curiosity rover “driver” Amy Hale of NASA’s Jet Propulsion Laboratory (JPL) in Southern California.

Though they are called rover drivers, Hale and 15 other rover drivers/planners don’t actually drive Curiosity. Instead, they write hundreds and hundreds of lines of code that are sent to Curiosity each day. These lines of code command Curiosity‘s mobility system and other instruments (i.e. robotic arm and drill) and provide the rover with a route to drive each day. Given that Curiosity is given commands once a day, a team of scientists and engineers must work together each day to discuss the area surrounding the rover and the best route for Curiosity to take the next day. Furthermore, this team not only discusses route options but also surrounding rock formations and surface features that scientists may want Curiosity to investigate up-close with cameras on its robotic arm.

When determining the route the rover will take the next day, the scientists and engineers need to look very carefully for hazards that may damage Curiosity while driving across the Martian surface. The teams look at Curiosity‘s images for any signs of hazardous rocks or sand that could puncture a wheel or lead to the rover getting stuck. In fact, some Curiosity scientists look at the images to ensure that no canyon walls or rock formations obstruct radio communications with Earth. If the teams identify a hazard, they inform the rover drivers who then program Curiosity to carefully maneuver around the hazard.

Though 23-degree inclines and wheel-sized rocks certainly sound frightening and dangerous for Curiosity, the rover’s teams back on Earth know the rover’s limits very well and never put the rover in dangerous situations. Even if they did, the rover is sent commands to immediately stop moving if it happens to find an unforeseen hazard. These unexpected stoppages, which are referred to as “faults” by the Curiosity team, happen often.

While climbing to and through Jau, Curiosity found its wheels slipping too much and being raised too high by rock formations fairly often. When these scenarios occurred, the rover’s computers detected that the rover may be in danger and immediately stopped all movement.

Image from Curiosity, during its climb through Jau, showing wheel tracks where a fault occured. (Credit: NASA/JPL-Caltech)

“We were basically playing fault bingo. Each day when we came in, we’d find out we faulted for one reason or another,” said Curiosity’s strategic route planning lead Dane Schoelen at JPL.

With Curiosity struggling with the original route too much, Schoelen and his team worked to put together a lateral detour that would have Curiosity drive 150 meters away to an area where the incline leveled out. While the team ultimately sent the command to Curiosity to take the detour, the team was still nervous that the terrain would not be exactly what it appeared to be. When planning routes and other rover activities, the teams utilize orbital imagery from NASA’s Mars Reconnaissance Orbiter (MRO) alongside Curiosity‘s images to plan routes. While orbital imagery can be efficient when planning routes, terrain height and other hazards aren’t immediately obvious in MRO imagery.

Fortunately, Schoelen et al.’s detour paid off and Curiosity successfully made its way to and through Jau.

“It felt great to finally get over the ridge and see that amazing vista. I get to look at images of Mars all day long, so I really get a sense of the landscape. I often feel like I’m standing right there next to Curiosity, looking back at how far it has climbed,” Schoelen said.

Since passing through Jau, scientists have begun investigating the region from data and imagery Curiosity collected of the region. Jau is a crater cluster, which are small clusters of craters caused by meteors breaking up in the Martian atmosphere before impact or fragments of distant meteoroid impacts. These crater clusters are common on Mars, and scientists are investigating how the soft rocks found within the salt-enriched terrain of the clusters affect the way the craters form and evolve.

With Jau now behind it, Curiosity will continue to climb up Mount Sharp and investigate the secrets Mars holds within its red soil. Mars is an extremely difficult place to simultaneously investigate and navigate, but with 11 years of roving underneath their belts, Curiosity and its incredible teams back on Earth show no signs of slowing down.

(Lead image: Curiosity stops to take a selfie while climbing Mount Sharp in 2021. Credit: NASA/JPL-Caltech/MSSS)

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