NASA/JPL-Caltech/ASU
The remains of a delta where a water source once fed an ancient lake in Jezero Crater. NASA’s Perseverance Rover is currently exploring the area.
Key points:
- Wandering the Red Planet. NASA’s Perseverance landed on Mars in February 2021 and has been collecting data on the planet’s geography and climate and searching for signs of ancient life.
- What lies beneath. The rover’s subsurface radar experiment, co-led by UCLA’s David Paige, has returned images that show unexpected variations in the rock layers beneath Jezero Crater.
- Probing the past. The variations could indicate past lava flows or possibly an even older fluvial delta than the one currently being explored on the crater floor.
After a tantalizing year-and-a-half wait since the Mars Perseverance Rover landed on our nearest planetary neighbor, new data is coming in, and it’s bringing some surprises.
The rover, which is about the size of a car and carries seven science instruments, has been probing Mars’ 30-mile-wide Jezero Crater, once the site of a lake and an ideal place to look for evidence of life old and information about the geological and climatic past of the planet.
In a paper published today in the journal Science Advances, a research team led by UCLA and the University of Oslo reveals that rock layers beneath the crater floor, observed by the rover’s ground-penetrating radar instrument , have an unexpected slant. The slopes, thicknesses, and shapes of the inclined sections suggest that they were formed by slowly cooling lava or were deposited as sediments in the ancient lake.
Perseverance is currently exploring a delta on the western rim of the crater, where a river once fed the lake, leaving behind a large deposit of dirt and rocks that it picked up along its course. As the rover gathers more data, researchers hope to shed light on the complex history of this part of the Red Planet.
Courtesy of David Paige
David Paige, Deputy Principal Investigator of Perseverance’s RIMFAX instrument.
“We were quite surprised to find rocks stacked at an inclined angle,” said David Paige, UCLA professor of Earth, planetary and space sciences and one of the principal investigators of the radar image for the Subsurface Experiment at Mars, or RIMFAX. “We expected to see horizontal rocks on the crater floor. The fact that they are tilted like this requires a more complex geological history. They could have formed when molten rock rose to the surface, or alternatively, they could represent an older deltaic deposit buried in the crater floor
Paige said most of the evidence collected by the rover so far points to an igneous or molten origin, but based on the RIMFAX data, he and the team still can’t say for sure how the tilted layers formed. RIMFAX obtains a picture of underground features by sending bursts of radar waves below the surface, which are reflected by layers of rock and other obstacles. The shapes, densities, thicknesses, angles and compositions of subsurface objects affect how the radar waves bounce, creating a visual image of what’s below.
During Perseverance’s initial 3-kilometer traverse, the instrument has obtained a continuous radar image that reveals the electromagnetic properties and bedrock stratigraphy (the arrangement of rock layers) of the Jezero floor at a depth of 15 meters, or about 49 feet. The image reveals the presence of ubiquitous layered rock strata, including those that are tilted up to 15 degrees. Adding to the mystery, within these tilted areas are some puzzling highly reflective rock layers that actually tilt in multiple directions.
“RIMFAX gives us a view of the stratigraphy of Mars similar to what can be seen on Earth in road cuts, where you can sometimes see tall stacks of rock layers on a mountain as you drive by,” explained Paige. “Prior to the Perseverance landing, there were many hypotheses about the exact nature and origin of the crater floor materials. We have now been able to narrow down the range of possibilities, but the data we have acquired so far suggests that the history of the crater floor may be a little more complicated than we had anticipated.”
NASA/JPL/Caltech/FFI
Rendering of Perseverance, whose RIMFAX technology is exploring what lies beneath the Martian surface.
The data collected by RIMFAX will provide valuable context to the rock samples being collected by Perseverance, which will eventually be brought back to Earth.
“RIMFAX offers us the background history of the samples we will analyze. It’s exciting that the rover’s instruments are producing data and we’re starting to learn, but there’s a lot more to come,” Paige said. “We landed on the crater floor, but now we’re driving into the actual delta, which is the goal principal of the mission. This is just the beginning of what we hope to soon learn about Mars.”
The paper, “Ground-penetrating radar observations of subsurface structures on the floor of Jezero Crater, Mars,” is one of three papers published simultaneously discussing some of Perseverance’s early data.
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