After a tantalizing year-and-a-half wait since the Mars Perseverance Rover
touched down on our nearest planetary neighbor, new data is arriving—and
bringing with it a few surprises.
The rover, which is about the size of car and carries seven scientific
instruments, has been probing Mars' 30-mile-wide Jezero crater, once the
site of a lake and an ideal spot to search for evidence of ancient life and
information about the planet's geological and climatic past.
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's floor, observed by the rover's ground-penetrating radar instrument,
are unexpectedly inclined. The slopes, thicknesses and shapes of the
inclined sections suggest they were either formed by slowly cooling lava or
deposited as sediments in the former lake.
Perseverance is currently exploring a delta on the western edge of the
crater, where a river once fed the lake, leaving behind a large deposit of
dirt and rocks it picked up along its course. As the rover gathers more
data, the researchers hope to clear up the complex history of this part of
the Red Planet.
"We were quite surprised to find rocks stacked up at an inclined angle,"
said David Paige, a UCLA professor of Earth, planetary and space sciences
and one of the lead researchers on the Radar Imager for Mars Subsurface
Experiment, or RIMFAX. "We were expecting to see horizontal rocks on the
crater floor. The fact that they are tilted like this requires a more
complex geologic history. They could have been formed when molten rock rose
up towards the surface, or, alternatively, they could represent an older
delta deposit buried in the crater floor."
Paige said that most of the evidence gathered by the rover so far points to
an igneous, or molten, origin, but based on the RIMFAX data, he and the team
can't yet say for certain how the inclined layers formed. RIMFAX obtains a
picture of underground features by sending bursts of radar waves below the
surface, which are reflected by rock layers and other obstacles. The shapes,
densities, thicknesses, angles and compositions of underground objects
affect how the radar waves bounce back, creating a visual image of what lies
beneath.
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
Jezero's floor to depths of 15 meters, or about 49 feet. The image reveals
the presence of ubiquitous layered rock strata, including those that are
inclined at up to 15 degrees. Compounding the mystery, within those inclined
areas are some perplexing highly reflective rock layers that in fact tilt in
multiple directions.
"RIMFAX is giving us a view of Mars stratigraphy similar to what you can see
on Earth in highway road cuts, where tall stacks of rock layers are
sometimes visible in a mountainside as you drive by," Paige explained.
"Before Perseverance landed, there were many hypotheses about the exact
nature and origin of the crater floor materials. We've now been able to
narrow down the range of possibilities, but the data we've acquired so far
suggest that the history of the crater floor may be quite a bit more
complicated than we had anticipated."
The data collected by RIMFAX will provide valuable context to rock samples
Perseverance is collecting, which will eventually be brought back to Earth.
"RIMFAX is giving us the backstory of the samples we're going to 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 up on the actual delta, which is
the main target of the mission. This is just the beginning of what we'll
hopefully soon know about Mars."
The paper, "Ground penetrating radar observations of subsurface structures
in the floor of Jezero crater, Mars," is one of three simultaneously
published papers discussing some of the first data from Perseverance.
Reference:
Svein-Erik Hamran et al, Ground penetrating radar observations of subsurface
structures in the floor of Jezero crater, Mars, Science Advances (2022).
DOI: 10.1126/sciadv.abp8564
Tags:
Space & Astrophysics