BLOGMARS PERSEVERANCE ROVER


How to Retain a Core
Mars Perseverance Sol 295 - Left Mastcam-Z Camera: In this image of a core we took in December, the core and the hole in the sample tube are offset from the hole in the coring bit.  This holds the core in the sample tube while the drill retracts from the rock. Credits: NASA/JPL-Caltech/ASU. Download image ›

Have you ever wondered how a coring bit grabs and holds onto a rock core?

As we drill, the bit teeth cut a 27mm diameter circle in the rock and leave the 13mm diameter center intact.  As we dig deeper, that cylinder of rock is fed into the sample tube that was loaded inside the bit.  When the drill reaches its target depth, typically 66mm, the core is fully inside the sample tube but may still be attached to the rock at the very bottom.  We need to:

  1. Snap the core off from the rock.
  2. Prevent the core from falling out of the bit as we retract from the hole.

We complete both tasks with a design called an eccentric sample tube.  It came from a NASA Small Business Innovation Research project with Honeybee Robotics.

This image shows the front of a sample tube.  From here you can see the wide side and the thin side.  The is the “eccentric” feature that lets the sample tube move into and out of alignment with the coring bit.
Mars Perseverance Sol 298 - Sample Caching System Camera: This image shows the front of a sample tube.  From here you can see the wide side and the thin side.  The is the “eccentric” feature that lets the sample tube move into and out of alignment with the coring bit. Credits: NASA/JPL-Caltech. Download image ›
It works like this: the coring bit walls have a wide side and a narrow side, and the sample tube walls have a wide side and a narrow side.  If you line up the wide side of the bit with the narrow side of the sample tube, the hole in the sample tube will be centered and line up with the hole in the front of the bit.  We call this “open”.  However, if you rotate the bit 180 degrees to line up the wide side of the bit with the wide side of the sample tube, it moves the hole in the sample tube out of the center and over to one side.  That means it won’t line up with the hole in the front of the bit.  We call this “closed”. 

The drill has a mechanism that can hold the sample tube in place while the bit rotates around it.  This lets us switch between open and closed.  We drill in the open position so the rock core can easily move into the tube.  At the bottom of the coring hole, right before we retract, we change to closed.  

If the core is still attached to the rock at that point, the act of closing will make the tube push on the core from one direction and the bit push on the core from the other direction.  That combination of forces will break the core off of the rock.  The core will then be fully inside the tube and bit, leaving behind just a short stump attached to the bottom of the hole.  The overlap between the bit and tube then serves its second function - it acts as a little ledge that holds the core inside the sample tube while the bit retracts from the hole.

It is possible for small pieces of core to fall through the hole between the bit and tube when they are in the closed position.  However, most cores we create are made of large pieces that are easy to retain.



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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Contributors+

  • Mariah Baker
    Planetary Scientist, Smithsonian National Air & Space Museum
    Washington, DC
  • Iona Brockie
    Sampling Engineer, NASA/JPL
    Pasadena, CA
  • 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
  • Alyssa Deardorff
    Systems Engineer, NASA/JPL
    Pasadena, CA
  • Kenneth Farley
    Project Scientist, Caltech
    Pasadena, CA
  • Phylindia Gant
    Mars 2020 Student Collaborator, University of Florida
  • Brad Garczynski
    Student Collaborator, Purdue University
    West Lafayette, IN
  • Erin Gibbons
    Student Collaborator, McGill University
    Montreal, Canada
  • Louise Jandura
    Chief Engineer for Sampling & Caching, NASA/JPL
    Pasadena, CA
  • Lydia Kivrak
    Student Collaborator, University of Florida
    Gainesville, FL
  • Rachel Kronyak
    Systems Engineer, NASA/JPL
    Pasadena, CA
  • Matt Muszynski
    Vehicle Systems Engineer, NASA/JPL
    Pasadena, CA
  • Avi Okon
    Sampling Operations Deputy Lead, NASA/JPL
  • 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
  • Vivian Sun
    Science Operations Systems Engineer, Staff Scientist, 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
  • Roger Wiens
    Principal Investigator, SuperCam / Co-Investigator, SHERLOC instrument, LANL
    Los Alamos, NM

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:


CAMERAS & SPECTROMETERS
GROUND-PENETRATING RADAR
ENVIRONMENTAL SENSORS
TECHNOLOGY DEMO
SAMPLE COLLECTION

Where is the Rover?

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

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