The escarpment the
science team refers to as “Scarp a” is seen in this image captured by
Perseverance rover’s Mastcam-Z instrument on Apr. 17, 2021. Credits:
NASA/JPL-Caltech/ASU/MSSS
Pictures from NASA’s latest six-wheeler on the Red Planet suggest the
area’s history experienced significant flooding events.
A new paper from the science team of NASA’s Perseverance Mars rover details
how the hydrological cycle of the now-dry lake at Jezero Crater is more
complicated and intriguing than originally thought. The findings are based on
detailed imaging the rover provided of long, steep slopes called escarpments,
or scarps in the delta, which formed from sediment accumulating at the mouth of
an ancient river that long ago fed the crater’s lake.
The images reveal that billions of years ago, when Mars had an atmosphere
thick enough to support water flowing across its surface, Jezero’s fan-shaped
river delta experienced late-stage flooding events that carried rocks and
debris into it from the highlands well outside the crater.
This image of an escarpment, or scarp – a long, steep slope – along the delta of Mars’ Jezero Crater was generated using data from the Perseverance rover’s Mastcam-Z instrument. The inset image at top is a close-up provided by the Remote Microscopic Imager, which is part of the SuperCam instrument. Credits: NASA/JPL-Caltech/LANL/CNES/CNRS/ASU/MSSS Full image and caption
Taken by the rover’s left and right Mastcam-Z cameras as well as its
Remote Micro-Imager, or RMI (part of the SuperCam instrument), they also provide
insight into where the rover could best hunt for rock and sediment samples,
including those that may contain organic compounds and other evidence that life
once existed there.
The rover team has long planned to visit the delta because of its potential
for harboring signs of ancient microbial life. One of the mission’s primary
goals is to collect samples that could be brought to Earth by the
multi-mission Mars Sample Return effort, enabling
scientists to analyze the material with powerful lab equipment too large to
bring to Mars.
The paper on Perseverance’s scarp imagery – the first research to be
published with data acquired after the rover’s Feb. 18 landing – was released
online today in the journal Science.
This annotated image indicates the locations of NASA’s Perseverance rover (lower right), as well as the “Kodiak” butte (lower left) and several prominent steep banks known as escarpments, or scarps, along the delta of Jezero Crater. Credits: NASA/JPL-Caltech/University of Arizona/USGS
Perseverance’s ‘Kodiak’ Moment
At the time the images were taken, the scarps were to the northwest of the
rover and about 1.2 miles (2.2 kilometers) away. Southwest of the rover, and at
about the same distance, lies another prominent rock outcrop the team calls
“Kodiak.” In its ancient past, Kodiak was at the southern edge of the delta,
which would have been an intact geologic structure at the time.
Prior to Perseverance’s arrival, Kodiak had been imaged only from orbit.
From the surface, the rover’s Mastcam-Z and RMI images revealed for the first
time the stratigraphy – the order and position of rock layers, which provides
information about the relative timing of geological deposits – along Kodiak’s
eastern face. The inclined and horizontal layering there is what a geologist
would expect to see in a river delta on Earth.
“Never before has such well-preserved stratigraphy been visible on Mars,”
said Nicolas Mangold, a Perseverance scientist from the Laboratoire de
Planétologie et Géodynamique in Nantes, France, and lead author of the paper.
“This is the key observation that enables us to once and for all confirm the
presence of a lake and river delta at Jezero. Getting a better understanding of
the hydrology months in advance of our arrival at the delta is going to pay big
dividends down the road.”
While the Kodiak results are significant, it is the tale told by the images
of the scarps to the northeast that came as the greatest surprise to the rover
science team.
This image of “Kodiak” – one remnant of the fan-shaped deposit of sediments inside Mars’ Jezero Crater known as the delta – was taken by Perseverance’s Mastcam-Z instrument on Feb. 22, 2021. Credits: NASA/JPL-Caltech/ASU/MSSS
Moving Boulders
Imagery of those scarps showed layering similar to Kodiak’s on their lower
halves. But farther up each of their steep walls and on top, Mastcam-Z and RMI
captured stones and boulders.
“We saw distinct layers in the scarps containing boulders up to 5 feet [1.5
meters] across that we knew had no business being there,” said Mangold.
Those layers mean the slow, meandering waterway that fed the delta must
have been transformed by later, fast-moving flash floods. Mangold and the
science team estimate that a torrent of water needed to transport the boulders
– some for tens of miles – would have to travel at speeds ranging from 4 to 20
mph (6 to 30 kph).
“These results also have an impact on the strategy for the selection of
rocks for sampling,” said Sanjeev Gupta, a Perseverance scientist from Imperial
College, London, and a co-author of the paper. “The finest-grained material at
the bottom of the delta probably contains our best bet for finding evidence of
organics and biosignatures. And the boulders at the top will enable us to
sample old pieces of crustal rocks. Both are main objectives for sampling and
caching rocks before Mars Sample Return.”
The annotated version of the mosaic indicates the location of four prominent escarpments, or scarps (long, steep slopes), along Jezero Crater’s river delta. The images were taken by the Mastcam-Z instrument aboard NASA’s Perseverance rover on April 17, 2021. Credits: NASA/JPL-Caltech/ASU/MSSS
A Lake of Changing Depths
Early in the history of the Jezero Crater’s former lake, its levels are
thought to have been high enough to crest the crater’s eastern rim, where
orbital imagery shows the remains of an outflow river channel. The new paper
adds to this thinking, describing the size of Jezero’s lake fluctuating greatly
over time, its water level rising and falling by tens of yards before the body
of water eventually disappeared altogether.
While it’s unknown if these swings in the water level resulted from
flooding or more gradual environmental changes, the science team has determined
that they occurred later in the Jezero delta’s history, when lake levels were
at least 330 feet (100 meters) below the lake’s highest level. And the team is
looking forward to making more insights in the future: The delta will be the
starting point for the rover team’s upcoming second science campaign next year.
“A better understanding of Jezero’s delta is a key to understanding the
change in hydrology for the area,” said Gupta, “and it could potentially
provide valuable insights into why the entire planet dried out.”
More About Perseverance
A key objective for Perseverance’s mission on Mars is astrobiology, including the search
for signs of ancient microbial life. The rover will characterize the planet’s
geology and past climate, pave the way for human exploration of the Red Planet,
and be the first mission to collect and cache Martian rock and regolith.
Subsequent NASA missions, in cooperation with ESA (European Space Agency),
would send spacecraft to Mars to collect these sealed samples from the surface
and return them to Earth for in-depth analysis.
The Mars 2020 Perseverance mission is part of NASA’s Moon to Mars
exploration approach, which includes Artemis missions to the
Moon that will help prepare for human exploration of the Red Planet.
JPL, which is managed for NASA by Caltech in Pasadena, California, built
and manages operations of the Perseverance rover.
For more about Perseverance: mars.nasa.gov/mars2020/ and nasa.gov/perseverance
Source: https://www.nasa.gov/feature/jpl/nasa-s-perseverance-sheds-more-light-on-jezero-crater-s-watery-past
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