Though once considered only a path free of obstacles that slow down rovers, Neretva Vallis has given the scientists team a plethora of geologic alternatives.
On June 9, NASA’s Perseverance Mars rover arrived at its most recent location of scientific interest after veering through a dune field to avoid pebbles that rattled wheels. The science team was able to discover intriguing geologic features in an old river channel in addition to cutting the projected travel time to that location—dubbed “Bright Angel”—by several weeks.
In search of carbonate and olivine deposits in the “Margin Unit,” a region inside the lip of Jezero Crater, Perseverance is nearing the end of its fourth scientific expedition. Bright Angel is a rocky area with light-toned outcrops near the base of the northern channel wall. These features could be sediments that filled the channel or old rock exposed by river erosion. In addition to looking for rocks that differ from those in the Margin Unit, which is rich in carbonate and olivine, the team hopes to learn more about Jezero’s past.
The Neretva Vallis river channel, which carried much of the water that spilled into Jezero Crater billions of years ago, was driven by the rover up a ridge to reach Bright Angel. “We were making pretty good progress paralleling the channel in late January, but then the boulders got bigger and more numerous,” stated Evan Graser, the deputy strategic route planner lead for Perseverance 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.”
Changing Channels
Evan and his crew plan drives of approximately 100 feet (30 meters) at a time using rover imagery in tough terrain. Planners depend on Perseverance’s auto-navigation system, also known as AutoNav, to take control in order to travel forward on every given Martian day, or sol.
But as the rocks proliferated, AutoNav would almost always decide the going was bad and stop, making it less likely that it would arrive at Bright Angel in time. Though they could succeed in cutting across a 400-meter (quarter-mile) dune field in the river channel, the team remained optimistic.
“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,” stated Graser. “Perseverance also needed an entrance ramp we could safely travel down. When the imagery showed both, we made a beeline for it.”
In order to study ancient Martian river systems, the science team at Perseverance was also excited to explore the ancient river channel.
Rock star
Perseverance reached the first science stop in one sol, traveling 656 feet (200 meters) with AutoNav assisting with navigation on the canal bottom. The objective was “Mount Washburn,” a hill covered in fascinating stones, some of which were unlike anything that had ever been seen on Mars.
According to Brad Garczynski of Western Washington University in Bellingham, who is co-leading the current science campaign, “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.” “But among all these different rocks, there was one that really caught our attention.” They gave it the moniker “Atoko Point.”
The flecked, pale boulder, measuring around 18 inches (45 centimeters) in width and 14 inches (35 centimeters) in height, sticks out among a sea of darker ones. The SuperCam and Mastcam-Z instruments of Perseverance have determined that the rock is primarily made of feldspar and pyroxene. Atoko Point is unmatched in terms of the dimensions, forms, and arrangements of its mineral grains and crystals, as well as possibly its chemical makeup.
They had never seen anything like it before, but this is the first.
Following its departure from Mount Washburn, the rover traveled 433 feet (132 meters) north to explore the geology of “Tuff Cliff” before traveling 1,985 feet (605 meters) in four sols to Bright Angel. Right now, Perseverance is examining a rocky outcrop to determine whether or not a rock core sample has to be taken.
