“Sombrero Rock”: A Case of Case-Hardening?
Mars Perseverance Sol 907 - Right Mastcam-Z CameraMastcam-Z image taken of Middle Mountain, nicknamed “sombrero rock”, as part of a multispectral observation on sol 907 to better understand its composition. This image was acquired on Sept. 8, 2023 (Sol 907) at the local mean solar time of 12:44:36. Credits: NASA/JPL-Caltech/ASU. Download image ›

Mars never fails to provide us with interestingly-shaped rocks, and recent observations have been no exception. The rock seen in this sol 907 Mastcam-Z image has captured the hearts and minds of our science team: our hearts for its sombrero-like shape, and our minds for the potential science implications behind it.

“Sombrero rock” (officially named Middle Mountain) was found along our journey to the carbonate-bearing Margin Unit covered in a previous blog.  One hypothesis for its sombrero-like shape is that this is due to a process known as case hardening. This is where the outer shell of an exposed rock surface hardens either due to chemical weathering and a relative softening of the interior, or hardening of the exterior due to the development of a rind. This can cause the interior of the rock to be preferentially eroded away, leaving behind interesting, hollowed-out looking shapes. Both versions of this case hardening process are often closely associated with near-surface water-rock interactions, and so this could have interesting implications for past climate and surface water on Mars.

NASA's Mars Perseverance rover acquired this image using its Right Mastcam-Z camera. Mastcam-Z is a pair of cameras located high on the rover's mast.
Mars Perseverance Sol 865 - Right Mastcam-Z CameraMastcam-Z image, taken as part of a wider contextual mosaic of the area, showing a hollowed-out looking rock on sol 865. This image was acquired on July 27, 2023 (Sol 865) at the local mean solar time of 15:36:11. Credits: NASA/JPL-Caltech/ASU. Download image ›

We’ve been seeing several examples of hollowed-out looking rocks through Perseverance’s traverse of the Upper Fan. These include the rocks seen in Mastcam-Z images on sol 865 and sol 836.

The sombrero-shaped Middle Mountain, first seen on sol 905, was targeted with both a SuperCam Laser Induced Breakdown Spectroscopy (LIBS) observation and a Mastcam-Z multispectral observation to assess its composition. Investigating whether there is a compositional difference between the inner core and outer rim of the “sombrero” may help us to understand the processes behind its distinct shape, therefore increasing our understanding of the geological history of this area further.

The rocks of Jezero crater continue to delight us!

About This Blog

These blog updates are provided by self-selected Mars 2020 mission team members who love to share what Perseverance is doing with the public.

Dates of planned rover activities described in these blogs are subject to change due to a variety of factors related to the Martian environment, communication relays and rover status.

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  • Mariah Baker
    Planetary Scientist, Smithsonian National Air & Space Museum
    Washington, DC
  • Matthew Brand
    SuperCam/ChemCam Engineer, Los Alamos National LaboratoryLos Alamos National Laboratory
  • Sawyer Brooks
    Docking Systems Engineer, NASA/JPL
    Pasadena, CA
  • Adrian Brown
    Deputy Program Scientist, NASA HQ
    Washington, DC
  • Denise Buckner
    Student Collaborator, University of Florida
    Gainesville, FL
  • Fred Calef III
    Mapping Specialist, NASA/JPL
    Pasadena, CA
  • Stephanie Connell
    SuperCam, PhD Student, Purdue University
    West Lafayette, IN
  • Alyssa Deardorff
    Systems Engineer, NASA/JPL
    Pasadena, CA
  • Kenneth Farley
    Project Scientist, Caltech
    Pasadena, CA
  • Phylindia Gant
    Mars 2020 Student Collaborator, University of Florida
    Gainesville, FL
  • Brad Garczynski
    Student Collaborator, Purdue University
    West Lafayette, IN
  • Erin Gibbons
    Student Collaborator, McGill University
    Montreal, Canada
  • Michael Hecht
    Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) Principal Investigator, Massachusetts Institute of Technology
    Westford, MA
  • Louise Jandura
    Chief Engineer for Sampling & Caching, NASA/JPL
    Pasadena, CA
  • Elisha Jhoti
    Ph.D. Student, University of California, Los Angeles
    Los Angeles, CA
  • Bavani Kathir
    Student Collaborator on Mastcam-Z, Western Washington University
  • Lydia Kivrak
    Student Collaborator, University of Florida
    Gainesville, FL
  • Athanasios Klidaras
    Ph.D. Student, Purdue University
  • Rachel Kronyak
    Systems Engineer, NASA/JPL
    Pasadena, CA
  • Steven Lee
    Perseverance Deputy Project Manager, NASA/JPL
    Pasadena, CA
  • An Li
    Student Collaborator on PIXL, University of Washington
  • Justin Maki
    Imaging Scientist and Mastcam-Z Deputy Principal Investigator, NASA/JPL
  • Forrest Meyen
    MOXIE Science Team Member, Lunar Outpost
  • Sarah Milkovich
    Assistant Science Manager, NASA/JPL
    Pasadena, CA
  • Eleanor Moreland
    Ph.D. Student, Rice University
    Houston, Texas
  • Asier Munguira
    Ph.D. Student, University of the Basque Country
  • Matt Muszynski
    Vehicle Systems Engineer, NASA/JPL
    Pasadena, CA
  • Claire Newman
    Atmospheric Scientist, Aeolis Research
    Altadena, CA
  • Avi Okon
    Sampling Operations Deputy Lead, NASA/JPL
    Pasadena, CA
  • Pegah Pashai
    Vehicle Systems Engineer Lead, NASA/JPL
    Pasadena, CA
  • David Pedersen
    Co-Investigator, PIXL Instrument, Technical University of Denmark (DTU)
    Copenhagen, Denmark
  • Eleni Ravanis
    Student Collaborator, University of Hawaiʻi at Mānoa
    Honolulu, HI
  • Thirupathi Srinivasan
    Robotic Systems Engineer, NASA/JPL
  • Kathryn Stack
    Deputy Project Scientist, NASA/JPL
    Pasadena, CA
  • Vivian Sun
    Science Operations Systems Engineer, Staff Scientist, NASA/JPL
    Pasadena, CA
  • Iona (Brockie) Tirona
    Sampling Engineer, NASA/JPL
    Pasadena, CA
  • Jennifer Trosper
    Project Manager, NASA/JPL
    Pasadena, CA
  • Vandi Verma
    Chief Engineer for Robotic Operations, NASA/JPL
    Pasadena, CA
  • Rick Welch
    Deputy Project Manager, NASA/JPL
    Pasadena, CA
  • Roger Wiens
    Principal Investigator, SuperCam / Co-Investigator, SHERLOC instrument, Purdue University
    West Lafayette, IN

Tools on the Perseverance Rover+

The Perseverance rover has tools to study the history of its landing site, seek signs of ancient life, collect rock and soil samples, and help prepare for human exploration of Mars. The rover carries:


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Image of a rover pin-point at Perseverance's location on Mars, Jezero Crater

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