NASA’s Perseverance fords an ancient river to achieve a scientific goal

Originally considered little more than a route free of rover-delaying boulders, Neretva Vallis has provided the scientific team with a plethora of geological options.

After taking a detour through a dune field to avoid rattling boulders, NASA’s Perseverance Mars rover reached its latest area of ​​scientific interest on June 9. The route change not only shortened the estimated driving time to reach that area, nicknamed ‘Bright Angel’, by several weeks, but also gave the science team the opportunity to find exciting geological features in an ancient river channel.

Perseverance is in the later stages of its fourth science campaign, looking for evidence of carbonate and olivine deposits in the ‘Margin Unit’, an area along the inner rim of Jezero Crater. Located at the base of the northern canal wall, Bright Angel has rocky, light-colored outcrops that may represent both ancient rocks exposed by river erosion and sediments that filled the canal. The team hopes to find rocks other than those in the carbonate- and olivine-rich Margin Unit and gather more clues about Jezero’s history.

To reach Bright Angel, the rover drove along a ridge along the Neretva Vallis river channel, which carried much of the water flowing into the Jezero crater billions of years ago. “We started paralleling the channel in late January and were making pretty good progress, but then the boulders got bigger and more numerous,” said Evan Graser, Perseverance’s deputy chief strategic route planner at NASA’s Jet Propulsion Laboratory in Southern California. “What used to be an average of more than a hundred meters per Martian day dropped to just tens of meters. It was frustrating.”

Zapping

In rugged terrain, Evan and his team use rover imagery to plan runs of about 100 feet at a time. To move forward on a given Martian day, or sol, planners rely on Perseverance’s automatic navigation system, or AutoNav, to take over.

But as the rocks became more plentiful, more often than not AutoNav concluded things weren’t going their way and stopped, dimming the prospects of an on-time arrival at Bright Angel. However, the team was hopeful as they knew they could achieve success by crossing a 400-metre dune field in the river channel.

“We had been checking out the river channel just to the north as we were traveling, hoping to find a section where the dunes were small and far enough apart for a rover to pass between them – because dunes are known to eat Mars rovers,” says Graser. . “Perseverance also needed a ramp where we could get down safely. When the footage showed both, we headed down there.”

The Perseverance science team was also keen to travel through the ancient river channel as they wanted to investigate ancient river processes on Mars.

Rock star

With AutoNav guiding the way on the canal floor, Perseverance covered the 200 meters to the first science stop in one sol. The target: ‘Mount Washburn’, a hill covered in intriguing boulders, some of which have never been seen before on Mars.

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

The speckled, light-colored boulder is about 18 inches wide and 14 inches high and stands out in a field of darker specimens. Analysis by Perseverance’s SuperCam and Mastcam-Z instruments indicates that the rock is composed of the minerals pyroxene and feldspar. In terms of the size, shape and arrangement of the mineral grains and crystals (and possibly also the chemical composition), Atoko Point is in a class of its own.

Some Perseverance scientists speculate that the minerals that make up Atoko Point were produced in an underground body of magma that may now be exposed on the crater rim. Others on the team wonder if the boulder originated far beyond the walls of Jezero centuries ago and was transported there by the swift waters of Mars. Regardless, the team believes that while Atoko is the first of its kind they’ve seen, it won’t be the last.

After leaving Mount Washburn, the rover headed 450 feet (132 meters) north to investigate the geology of “Tuff Cliff” before making the four-sol, 605-meter (1,985 feet) journey to Bright Angel. Perseverance is currently analyzing a rock outcrop to assess whether a rock core sample should be collected.