NASA's Perseverance rover has left Mount Washburn behind and arrived at its next destination, Bright Angel, where it has found an unusual type of rock that scientists call “popcorn rock.” The strange rock is further evidence that water was once present in Jezero Crater.
Perseverance's mission is focused on life on ancient Mars. In addition to looking for fossilized evidence of ancient life, the probe is also searching for and trying to understand environments that might have supported life. That's why it is located in Jezero Crater, an ancient paleolake with a sedimentary delta and other fascinating geological features.
On sol 1175 of its mission, Perseverance arrived at Bright Angel, a region of scientific interest that is part of the river channel that flows into Jezero Crater. Bright Angel is known for its bright rock outcrops, which are either composed of ancient sediments that filled the channel or of much older rock exposed by the river.
The image below shows the rover's path leading to Bright Angel. The white part shows where Perseverance paralleled the Neretva Vallis riverbed, and the blue part shows where it drove through the bed. The bright rocks of Bright Angel are clearly visible.
This Mars Reconnaissance Orbiter image, taken with the orbiter's HiRISE camera, shows the Neretva Vallis river channel with Perseverance's path above it. The orbiter has passed Mount Washburn and reached Bright Angel. Image credit: NASA/JPL-Caltech/University of Arizona
As Perseverance moved toward Bright Angel, mission crews could see the bright rocks in the distance. But the path to the new destination was not easy. The rover encountered a boulder field that proved so difficult that the crew changed course.
“We started traveling parallel to 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 strategic route planning lead at NASA's Jet Propulsion Laboratory in Southern California. “The average travel distance of over 100 meters per Martian day was reduced to just a few tens of meters. It was frustrating.”
Perseverance has two modes of travel. In rougher terrain, the route planning team uses imagery to plan the rover's route in 30-meter increments. To get further in a single sol, the team relies on Perseverance's autopilot mode, called AutoNav. But as the route through the scree field became more difficult, AutoNav ran into trouble. Sometimes it just stopped, which is the safest option. But that meant the drive to Bright Angel took much longer than expected.
“We had been keeping an eye on the river channel 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 drive through — because dunes are known to eat Mars rovers,” Graser said. “Perseverance also needed an access ramp that we could drive down safely. When the images showed both, we headed straight for that.”
The rover was diverted through the dune field and across the river channel, shortening its journey by several weeks.
Perseverance captured this image of Bright Angel with one of its navcams on June 6, 2024. Bright Angel is the bright area in the distance to the right. Image credit: NASA/JPL-Caltech
Perseverance is nearing the end of its fourth exploration phase. It has been looking for carbonate rocks and olivine in the Margin Unit, which is located on the inside of the Jezero Crater rim. But at Bright Angel, it hoped to find other rocks.
That's exactly what happened.
According to a NASA press release, geologists were intrigued by what they saw. Some of the rocks are densely packed with balls, earning them the name “popcorn rocks.” The rocks are also full of ridges that look like mineral veins. Mineral veins are formed when water carries minerals through rock and deposits them.
These rocks in Bright Angel have unusual popcorn-like textures and numerous mineral veins. Image credit: NASA/JPL-Caltech/ASU
Mineral veins are common on wet, watery Earth, and rovers have discovered them elsewhere on Mars.
The MSL Curiosity Rover captured this image of mineral veins in Martian rocks in 2015. The area is called Garden City and is located at the base of Mount Sharp in Gale Crater. Image credit: NASA/JPL-Caltech/MSSS
The popcorn structures could also be evidence of water. Like the mineral veins, they indicate that water has flowed through these rocks.
The next step is to determine what minerals are present in these popcorn rocks. Perseverance will work its way up to Bright Angel, taking measurements as it goes. Over the weekend, it will use its abrasion tool and other instruments to look even closer. It will vaporize some of the rock and use its SuperCam suite of instruments to study the rock's chemistry. The decision to take a sample and (hopefully) return to Earth will depend on those results.
Once Perseverance finishes at Bright Angel, the rover will head south again, through the Neretva Valley, to its next destination: Serpentine Rapids.
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