At Long Last, Perseverance Reaches Three Forks River Delta
After more than a year mapping the surface of Mars, NASA’s Perseverance rover has finally reached the ancient Martian river delta it was built to explore.
Perseverance and its companion space helicopter, Ingenuity, landed in Mars’ Jezero Crater in February of 2021. Since then, the rover has carefully picked its way around the rim of Jezero, scooping up samples and mapping its surroundings as it goes. Perseverance and Ingenuity have spent their time making parallel progress on their directives. Ingenuity even makes its own scientific sorties away from the rover. But Perseverance is drawing near its target.
The rover’s “Delta Front Campaign” is its second sortie, and the mission began this week. Among other scientific goals, NASA is using this campaign to scope out the best route to ascend the Three Forks river delta.
Mission scientists chose Jezero Crater because it was loaded with telltale signs that once upon a time, it held an ancient lake. For one, the basin of the crater is loaded with montmorillonite clay. Clay is a product of silicate weathering in the presence of water. For another, there’s a place on the crater’s edge where you can see that the wall has crumbled. Colorful streaks of sediment fan out from that gap in the wall, looking just like Earthly river deltas.
“The delta is why Perseverance was sent to Jezero Crater: It has so many interesting features,” explained Ken Farley, a Perseverance project scientist at Caltech. “We will look for signs of ancient life in the rocks at the base of the delta, rocks that we think were once mud on the bottom of ‘Lake Jezero.’”
On Earth, water is life. Shallow pools of water incubated the alpha versions of so many different forms of life. Even the driest desert ecosystems can thrive, because living things can use the water droplets in fog, or the water that condenses on cooler sand beneath the surface. Consequently, scientists reason that our best shot at finding signs of life off-world is following traces of liquid water.
“The delta at Jezero Crater promises to be a veritable geologic feast and one of the best locations on Mars to look for signs of past microscopic life,” said Thomas Zurbuchen, of NASA’s Science Mission Directorate. “The answers are out there – and Team Perseverance is ready to find them.”
Right now Perseverance is in the middle of a week-long, 3-mile (5-km) drive to the southwest. Mission scientists expect rover’s Delta Front Campaign to take about half an Earth year. At that point, Perseverance will have to make a choice.
Three Forks, the Perseverance rover’s scientific target, is named for its terrain. It’s a climb of about 130 feet (40 meters) to the top of the delta from the crater floor. There are three main paths from the bottom of Jezero Crater to the top of the Three Forks delta. Unfortunately, only two of them, called “Cape Nukshak” and “Hawksbill Gap,” look passable. Currently, NASA said in a statement, the Perseverance science team is “leaning toward Hawksbill Gap,” because that’s the path with the shorter drive time. However, that may change as we learn more about the rover’s options.
“We’ve been eyeing the delta from a distance for more than a year while we explored the crater floor,” said Farley. “At the end of our fast traverse, we are finally able to get close to it, obtaining images of ever-greater detail revealing where we can best explore these important rocks.”
“Higher up the delta, we can look at sand and rock fragments that came from upstream, perhaps from miles away. These are locations the rover will never visit. We can take advantage of an ancient Martian river that brought the planet’s geological secrets to us.”