NASA’s Perseverance rover puts its robotic arm to work around a rocky outcrop called “Skinner Ridge” in Mars’ Jezero Crater. Composed of multiple images, this mosaic shows layered sedimentary rocks in the face of a cliff in the delta, as well as one of the locations where the rover abraded a circular patch to analyze a rock’s composition. Credits: NASA/JPL-Caltech/ASU/MSSS
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NASA’s Perseverance rover is well into its second science
campaign, collecting rock-core samples from features within an
area long considered by scientists to be a top prospect for finding signs of
ancient microbial life on Mars. The rover has collected four samples from an
ancient river delta in the Red Planet’s Jezero Crater since July 7, bringing
the total count of scientifically compelling rock samples to 12.
“We picked the Jezero Crater for Perseverance to explore because we thought
it had the best chance of providing scientifically excellent samples – and now
we know we sent the rover to the right location,” said Thomas Zurbuchen, NASA’s
associate administrator for science in Washington. “These first two science
campaigns have yielded an amazing diversity of samples to bring back to Earth
by the Mars Sample Return campaign.”
Twenty-eight miles (45 kilometers) wide, Jezero Crater hosts a delta – an
ancient fan-shaped feature that formed about 3.5 billion years ago at the
convergence of a Martian river and a lake. Perseverance is currently
investigating the delta’s sedimentary rocks, formed when particles of various
sizes settled in the once-watery environment. During its first science campaign, the rover explored the crater’s floor, finding igneous rock, which forms deep underground from magma or during volcanic activity at
the surface.
“The delta, with its diverse sedimentary rocks, contrasts beautifully with
the igneous rocks – formed from crystallization of magma – discovered on the crater floor,” said Perseverance project scientist Ken Farley of Caltech in Pasadena,
California. “This juxtaposition provides us with a rich understanding of the
geologic history after the crater formed and a diverse sample suite. For
example, we found a sandstone that carries grains and rock fragments created
far from Jezero Crater – and a mudstone that includes intriguing organic
compounds.”
“Wildcat Ridge” is the name given to a rock about 3 feet (1 meter) wide
that likely formed billions of years ago as mud and fine sand settled in an
evaporating saltwater lake. On July 20, the rover abraded some of the surface
of Wildcat Ridge so it could analyze the area with the instrument called
Scanning Habitable Environments with Raman & Luminescence for Organics
& Chemicals, or SHERLOC.
SHERLOC’s analysis indicates the samples feature a class of organic
molecules that are spatially correlated with those of sulfate minerals. Sulfate
minerals found in layers of sedimentary rock can yield significant information
about the aqueous environments in which they formed.
What Is Organic Matter?
Organic molecules consist of a wide variety of compounds made primarily of
carbon and usually include hydrogen and oxygen atoms. They can also contain
other elements, such as nitrogen, phosphorus, and sulfur. While there are
chemical processes that produce these molecules that don’t require life, some
of these compounds are the chemical building blocks of life. The presence of
these specific molecules is considered to be a potential biosignature – a
substance or structure that could be evidence of past life but may also have
been produced without the presence of life.
In 2013, NASA’s Curiosity Mars rover found evidence of organic
matter in rock-powder samples, and Perseverance
has detected organics in Jezero Crater before. But unlike that previous discovery, this latest
detection was made in an area where, in the distant past, sediment and salts
were deposited into a lake under conditions in which life could potentially
have existed. In its analysis of Wildcat Ridge, the SHERLOC instrument
registered the most abundant organic detections on the mission to date.
“In the distant past, the sand, mud, and salts that now make up the Wildcat
Ridge sample were deposited under conditions where life could potentially have
thrived,” said Farley. “The fact the organic matter was found in such a
sedimentary rock – known for preserving fossils of ancient life here on Earth –
is important. However, as capable as our instruments aboard Perseverance are,
further conclusions regarding what is contained in the Wildcat Ridge sample
will have to wait until it’s returned to Earth for in-depth study as part of
the agency’s Mars Sample Return campaign.”
The first step in the NASA-ESA (European Space Agency) Mars Sample Return
campaign began when Perseverance cored its first rock
sample in September 2021. Along with its rock-core
samples, the rover has collected one atmospheric sample and two witness tubes, all of which are stored in the rover’s belly.
The geologic diversity of the samples already carried in the rover is so
good that the rover team is looking into depositing select tubes near the base
of the delta in about two months. After depositing the cache, the rover will
continue its delta explorations.
“I’ve studied Martian habitability and geology for much of my career and
know first-hand the incredible scientific value of returning a carefully
collected set of Mars rocks to Earth,” said Laurie Leshin, director of NASA's
Jet Propulsion Laboratory in Southern California. “That we are weeks from
deploying Perseverance’s fascinating samples and mere years from bringing them
to Earth so scientists can study them in exquisite detail is truly phenomenal.
We will learn so much.”
More About the Mission
A key objective for Perseverance’s mission on Mars is astrobiology, including caching
samples that may contain 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, 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, built and manages operations of the Perseverance rover.
For more about Perseverance: https://mars.nasa.gov/mars2020/
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