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The Perseverance rover has begun a long climb up the steep rim of Jezero Crater, searching for some of the oldest rocks on Mars and exploring the potential of environments on the Red Planet that could once have supported life.
The robotic explorer landed in Jezero Crater 3 1⁄2 years ago and has since explored the site of an ancient lake and river delta and collected countless rock samples. But its latest scientific journey could rewrite the way astronomers understand Mars.
“Perseverance has completed four science campaigns, collected 22 rock cores and traveled more than 18 unpaved miles (29 kilometers),” said Art Thompson, Perseverance project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California, in a statement. “As we begin the Crater Rim Campaign, our rover is in excellent shape and the team is eager to see what’s on the roof of this site.”
The rover will use its self-navigation capabilities, which allow Perseverance to function like a self-driving car, to follow a route planned by the vehicle’s engineers. The route will allow the rover to avoid hazards during the challenging climb. Perseverance will gain about 1,000 feet (300 meters) in altitude when it reaches the top of the ridge in late 2024.
Scientists have been anticipating this rise for years, long before Perseverance landed on Mars.
About 4 billion years ago, an object struck Mars and formed the Jezero crater. The impact sent huge boulders into the crater rim.
“We should be able to access and sample some of the oldest rocks on Mars in the crater rim,” said Briony Horgan, a co-investigator on the Perseverance rover mission and a professor of planetary sciences at Purdue University in West Lafayette, Indiana.
“We think this includes everything from ancient sedimentary rocks that could preserve the earliest habitable environments on Mars, to the building blocks of the planet that formed the earliest crust at the dawn of the solar system.”
The crater rim offers a glimpse into the earliest period of Mars’ history and could yield evidence of hot springs that may have supported ancient microbial life, Horgan said.
Back to time on Mars
The impact that created Jezero Crater also generated a lot of heat, partly from the energy of the object hitting Mars. Some of the heat also came from hotter rocks that were beneath the Martian surface, since the planet was still cooling after forming half a billion years earlier. The impact shook those rocks up from beneath the Martian surface.
If groundwater or surface water were present on Mars at the time, as scientists believe is likely, there would have been hydrothermal systems, said Ken Farley, a Perseverance project scientist and professor of geochemistry at the California Institute of Technology.
In hydrothermal systems, hot water likely circulated through cracks in the rocks, possibly creating the right environment for microbial life.
So far, Perseverance has explored the location of the ancient lakebed and river delta where life could have existed. The Pico Turquino crater rim site, as the hydrothermal rocks are called, offers another, different possibility.
“As part of the overall mission objectives, searching for evidence of possible life on Mars is high on the agenda, so we want to explore as many potentially habitable environments as possible that Mars has to offer,” Farley said.
The science team is also eager to reach Witch Hazel Hill, a large outcropping of black-and-white layered rocks that stretches for hundreds of meters. These layers of rocks may preserve information about the Martian climate billions of years ago. The rover should arrive there in six to nine months.
Plate tectonics and other erosion processes have swept away some of the oldest rocks on Earth. Yet, ancient rocks that reflect the history of Mars can still be found on the Red Planet.
The solar system formed 4.55 billion years ago, and the science team expects to find and study Martian rocks that are 4.2 billion years old, Farley said.
Climbing the crater
During the long drive up the crater wall, Perseverance could encounter slopes as steep as 23 degrees. Normally, the team avoids any route that tilts the rover more than 30 degrees. But the rover is well-prepared for the climb and is in no danger, Farley said.
“Climbing up to the crater rim would be quite a challenge for us humans, but from a rover standpoint it actually wouldn’t be that big of a deal,” said Steven Lee, Perseverance deputy project manager.
However, the rover’s progress could slow if it detects its wheels slipping on Martian terrain or if it encounters large boulders during its climb.
Perseverance can monitor the terrain as it drives, and if the wheels start to slip too much, the rover will stop and “call home for Mom, wait to be told what to do, and then we’ll figure it out on the ground,” Lee said.
The rover remains in excellent condition, and “there is no evidence that we cannot continue to use this vehicle for many years to come,” Lee said.
By the time the rover reaches the top of the ridge, it will have traveled tens of kilometers and captured countless new images for the mission team to analyze.
“It’s a unique perspective for those of us who work on the project every day,” Lee said. “You quickly start to get a sense of Mars as a place. My memories of Perseverance’s passes are a lot like memories of a walk. I can actually imagine what Mars looks like from the landing site to where we are now.”
And the rover’s view of the 45-kilometer-wide crater offers some stunning vistas.
“We definitely get to see some fantastic views looking back to where we came from in Jezero and the plains beyond,” Horgan said.
The biggest challenge for the science team will be deciding which rocks to study up close and which to collect samples from. With so many intriguing piles of rocks the size of school buses, the team will need to learn as much as possible while keeping the rover moving.
“All that stuff is just being thrown out in front of us,” Farley said, “so I think it’s going to be a very different kind of exploration.”
The team expects Perseverance to remain beyond the crater rim for a few more years to collect samples.
Meanwhile, the question of how those samples, along with those Perseverance collected in the crater, will return to Earth is looming as NASA reevaluates its Mars Sample Return program. The agency is evaluating several proposals and is expected to announce a decision in the fall.
The decision could determine how long and how far the rover drives, as the vehicle could be responsible for delivering samples to a spacecraft that then returns them to Earth.
“This part of the mission is essential to creating a sample collection that is the collection that everyone dreams of,” Farley said. “For now, we’re just going to continue our exploration of the crater rim. And when the time comes, we’ll do whatever we need to do to support Mars Sample Return.”
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