Mapping Mars rover Perseverance’s path as it collects rock samples

NASA’s Mars rover, Perseverance, aims for dicey landing to search for ancient life

The Perseverance rover is essentially a high-tech astrobiologist and geologist, equipped to investigate the geologic history and past climate of this corner of the crater. Three years into its exploration, the rover has traveled more than 15 miles exploring the crater floor, risen up the fan front and is now exploring along the edge of the ancient river inlet that, billions of years ago, allowed water to fill the crater. NASA has divided this journey through geologic time into 5 campaigns of exploration:

Considering that the rover can only travel 152 meters per hour (a little less than 0.1 mph), it has covered quite a distance. When contemplating the path the rover has taken over the past 3 years on a planet surface devoid of any contextual relationship for us here on Earth, it might help to consider the path over a more familiar terrain.

NASA was expecting the rover to land much closer to the fan front but the landing site wound up being a blessing in disguise, research scientist Katie Stack Morgan explained, because it allowed the team to realize that Perseverance was near some unexpected yet intriguing volcanic or igneous rock at the crater floor, which was worth going out of its way to explore. Stack Morgan works at NASA’s Jet Propulsion Laboratory at Caltech and is the deputy project scientist of the Mars 2020 rover mission.

Perseverance’s team spent the first 90 sols (Mars’s days are about 40 minutes longer than Earth’s) testing all the rover’s parts and instruments, before allowing it to move and collect the first of its 38 titanium sample tubes. Although the first sample taken by the rover wound up being an air sample (the Martian atmosphere is 96 percent carbon dioxide), the next eight samples collected were igneous rock cores.

Once the NASA team chooses a rock to consider for sampling, the drilling process begins. First, the rover cuts an abrasion patch, essentially scraping away the upper part of a rock; after the patch is cleared of the residual dust, it can be analyzed further by geologists. If the scientists decide to take a sample, the rover switches to a drill that cuts roughly 2 inches into the rock. Then the rover breaks off the sample and hermetically seals it in a tube. The tubes are placed on a storage rack in the belly of the rover.

After passing back by the original landing site, the rover went on a four-month rapid traverse across very smooth terrain. It conducted little science as it focused on reaching the fan front, where there was expected to be a major geologic transition from igneous rocks to more sedimentary rocks. Once Perseverance reached the area, the rover began a meandering path going back and forth along the front. It was “doing what geologists do,” Stack Morgan said, exploring multiple areas and returning back to outcrops previously explored.

Ultimately, over a five-month period, nine samples were collected — seven sedimentary rock cores and two samples of regolith, or loose material. Preliminary analysis by the rover team back on Earth showed the core samples represent river, delta and lake bed environments.

This portion of the campaign also highlights the long-term strategic planning NASA implements when operating a rover 140 million miles away. Through these first two campaigns, Perseverance had been collecting rock-core samples essentially in pairs as part of a contingency plan.

Arrangements are being made to bring these samples to Earth in the early or mid-2030s as part of a partnership with the European Space Agency. But, during this campaign, a contingency plan NASA calls depot caching was employed to leave the duplicate samples on the planet’s surface. From Dec. 21, 2022, to Jan. 28, 2023, the rover placed 10 sample tubes, between 15 to 50 feet apart, in a carefully mapped zigzag pattern. The Jezero Crater depot, dubbed the Three Forks, is now a ready backup in the event Perseverance cannot deliver the samples to Earth.

Last week, NASA’s Jet Propulsion Laboratory announced layoffs related to the mission of returning Martian samples back to Earth. JPL pointed to funding uncertainties and the failure of Congress to pass a 2024 budget for NASA.

Congressional budget gridlock leads to stunning NASA layoffs

However, Dewayne Washington, senior communications manager for the Mars Sample Return, said this week, “NASA has set up an independent review team to evaluate the Mars Sample Return Program, which will lay out a clear timeline and plan for the mission, with the best possible budgetary outlook. The agency has delayed its plans to confirm the official mission cost and schedule until after completion of the review, expected in March.”

When Perseverance landed on Mars, it carried NASA’s first helicopter in space, Ingenuity, which was to test the feasibility of flying on remote planets.

The helicopter proved to be a capable partner, flying slightly in advance of the rover. It captured video of the surface and provided more material for scientists on Earth to consider when deciding where to take Perseverance. One such flight led the team to redirect the rover and uncover the youngest rock sample collected thus far, fulfilling an important goal of acquiring not just different rock types but rocks from different ages.

On Jan. 25, NASA announced that on its last flight a week before, Ingenuity damaged a rotor and is no longer operational. Ingenuity was designed to fly only five times, but exceeded operational expectations with 72 flights covering 11 miles.

The samples collected in this campaign showed evidence the rocks were deposited by rivers. The three samples taken in this campaign included the first collection of rock conglomerate, which is composed of pebble-sized grains cemented together. This conglomerate was formed outside of the crater and carried into the fan by fast-moving water.

Perseverance’s current campaign is the margin unit, essentially the “inside margin” of the Jezero Crater rim. Imagery of Mars from previous orbital missions has shown strong evidence of carbonate deposits in this unit. “Carbonate is an important mineral for capturing and understanding the atmosphere of Mars, the interaction between the atmosphere and water at the surface of Mars, and also is a very bio-relevant mineral, at least on Earth,” Stack Morgan explained. “So carbonates are an excellent mineral to bring back from Mars, both from a geologic history perspective and understanding the evolution of the atmosphere in the surface, but also for astrobiology reasons as well.”

Planned crater rim campaign

For its next campaign, Perseverance will continue following the ancient river bed toward the mouth of the inlet that breaks through the canyon rim. Campaign planning has begun, and scientists have found a favorable slope up the rim that the rover most likely will take out of the crater. As Perseverance moves up the rim, scientists expect the geology will change in type and age as it moves away from the influences of the water forces that formed the fan and crater floor below.

The rover has 15 sample tubes remaining. It’s possible the decision-making on when to use the remaining tubes may become fraught, because scientists can’t sample every rock they find interesting.

But, Stack Morgan said, “given the realities of operating a Mars rover on the surface, we tend to think that the greater risk is that we may not fill them all, because rover progress can be slow. We’ve specifically tried to minimize that feeling of the tubes as so precious that the bar has to be incredibly high to use them and instead allow ourselves to say, ‘Yes, this rock is interesting.’ I think that approach has allowed us to maintain good progress in our sampling objectives.”

How much more can Perseverance explore?

Most of the hardware on the rover and the rover itself is qualified to 1½ Mars years, or about three Earth years, which it will be nearing in February, Stack Morgan said. While there are lots of unknowns, she said, “there’s the hope and the expectation that Perseverance would be able to continue for many more years. On the other hand, there’s also this timeline of when Perseverance would need to be in position to rendezvous with future sample-collection missions. That directive in a couple of months will very much crystallize what our future mission is going to look like.”

Path data and imagery were provided by NASA, U.S. Geological Survey, JPL-Caltech. D.C. vector data provided by D.C. Geographic Information System. Graphics editing by Samuel Granados and copy editing by Melissa Ngo.