Perseverance Reaches Key Target in Ancient Riverbed

Initially considered a simple route free of obstructions, Neretva Vallis has presented numerous geological opportunities for the science team. After navigating through a dune field to avoid challenging boulders, NASA’s Perseverance Mars rover arrived at its latest area of interest on June 9. The route change not only reduced travel time to the “Bright Angel” site by several weeks but also allowed the team to explore significant geological features in an ancient river channel.

Perseverance followed a ridge along the Neretva Vallis river channel, which once carried water into Jezero Crater. “We started paralleling the channel in late January and were making pretty good progress, but then the boulders became bigger and more numerous,” said Evan Graser, Perseverance’s deputy strategic route planner at NASA’s Jet Propulsion Laboratory in Southern California. “What had been drives averaging over a hundred meters per Martian day went down to only tens of meters. It was frustrating.”

In difficult terrain, the team uses rover imagery to plan drives of about 30 meters at a time. To go farther in a single Martian day, planners use Perseverance’s auto-navigation (AutoNav) system. However, as rocks became more frequent, AutoNav often halted the rover. The team decided to cross a 400-meter dune field in the river channel, hoping for better conditions.

“We had been eyeing the river channel just to the north as we went, hoping to find a section where the dunes were small and far enough apart for a rover to pass between – because dunes have been known to eat Mars rovers,” said Graser. “Perseverance also needed an entrance ramp we could safely travel down. When the imagery showed both, we made a beeline for it.”

The science team was also eager to explore the ancient river channel to investigate ancient Martian river processes.

With AutoNav guiding the way, Perseverance covered 200 meters to the first science stop in one sol. The target was Mount Washburn, a hill with diverse boulders, some never seen before on Mars.

“The diversity of textures and compositions at Mount Washburn was an exciting discovery for the team, as these rocks represent a grab bag of geologic gifts brought down from the crater rim and potentially beyond,” said Brad Garczynski of Western Washington University, co-lead of the current science campaign. “But among all these different rocks, there was one that really caught our attention.” They nicknamed it Atoko Point.

The 45-centimeter wide and 35-centimeter tall, light-toned boulder stood out. Analysis by Perseverance’s SuperCam and Mastcam-Z instruments showed it is composed of pyroxene and feldspar. Its mineral grains and crystals, and potentially its chemical composition, make Atoko Point unique.

Some scientists speculate that Atoko Point’s minerals were produced in a subsurface body of magma, now exposed on the crater rim. Others believe the boulder might have been transported by Martian waters from far beyond Jezero. Either way, the team expects to find more such rocks.

After Mount Washburn, the rover traveled 132 meters north to study the Tuff Cliff geology before making a 605-meter journey to Bright Angel. Perseverance is currently analyzing a rocky outcrop to decide if a rock core sample should be collected.