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NASA’s Mars Perseverance “Kodiak” Moment – Jezero Crater’s Lake Is More
Complicated and Intriguing Than Thought

TOPICS:AstrobiologyJPLMarsMars 2020 Perseverance RoverNASA
By JET PROPULSION LABORATORY OCTOBER 8, 2021

Jezero Crater's Scarp A
The escarpment the science team refers to as “Scarp a” is seen in this
image captured by Perseverance rover’s Mastcam-Z instrument on April 17,
2021. Credit: 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.

Mars Jezero Crater Delta Scarp
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: RMI: NASA/JPL-Caltech/LANL/CNES/CNRS/ASU/MSSS

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.

Perseverance Rover, Scarp, and Kodiak Locations
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. Credit: NASA/JPL-Caltech/University of Arizona/USGS

The paper on Perseverance’s scarp imagery – the first research to be
published with data acquired after the rover’s February 18 landing – was
released online today in the journal Science.

“This is the key observation that enables us to once and for all confirm
the presence of a lake and river delta at Jezero.”

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.

Mastcam Z Spots Remnant of a Fan Shaped Deposit of Sediments
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 February 22, 2021. Credit:
NASA/JPL-Caltech

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.

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.

Jezero Crater’s River Delta Mosaics
The top mosaic of Jezero Crater’s river delta was stitched together from
multiple images taken by the Mastcam-Z instrument aboard NASA’s
Perseverance rover on April 17, 2021. The bottom annotated image
highlights the location of four prominent long, steep slopes known as
escarpments, or scarps. Credit: NASA/JPL-Caltech/ASU/MSSS

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.”

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.

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