If your name begins with “L” you will especially enjoy this story about the first letter to be laser engraved on
However, as SuperCam’s predecessor had written a lengthy sequence that would use the laser to spell out the instrument’s name on the rock surface. It was all in fun—we never actually wasted our shots using that sequence. However, on Perseverance, we have found a reason to use laser marking.
Mars Perseverance Sol 471 – SuperCam Camera: Three dark laser pits in the shape of a slightly tilted letter “L” were produced in the rock surface of target “Pinefield Gap” (Sol 471) as a dry run for marking the surface of a sample core. The L mark is a way to maintain knowledge of the rotational orientation of the rock after the core is cut from the same location. The original orientation of the surface of the core will be useful to understand the original directions of magnetic domains in the samples after they are brought back to Earth. The L is 2.5 mm tall by 1.0 mm long (0.1” x 0.04”). The SuperCam instrument produced the laser pits using 125 shots in each pit, and also took this image. Credit: NASA/JPL-Caltech/LANL/CNES/IRAP
About two years ago I received a call from Professor Ben Weiss from the Massachusetts Institute of Technology (
To do that, for each Mars rock core sample that is returned, we need to know its original orientation on the planet. If the surfaces of those core samples have easily recognizable features, that’s no problem. That has been the case with the cores collected so far. However, if the surface is fine-grained, there may be nothing to distinguish its rotational orientation. In that case, we need to make artificial markings on the surface.
Mars Perseverance Sol 498 – Right Mastcam-Z Camera: Image taken by the Mastcam-Z right camera taken on Sol 498 showing the two drill holes and abrasion patch on the Skinner Ridge rock surface. Credit: NASA/JPL-Caltech/ASU
We don’t have a dark marker pen available, but we do have a pulsed laser on the SuperCam. So Ben’s call to my lab a couple of years ago got us thinking about how to mark the sample cores, and we started some tests. JPL shipped several rocks of varying hardness to Los Alamos National Laboratory where they were marked with pits made with different numbers of laser shots. The rocks were sent back to JPL for subsequent coring.
Fast forward to summer 2022. The SuperCam team was asked to be ready to mark a rock for coring with just a few days of notice. I was on SuperCam operations, and seeing how soon we might need the marks, we decided to switch from a normal observation to a core-marking sequence as a dry run. We had prepared various patterns for the mark. The basic principle is to understand the rotational orientation of the core after it has been removed from the rock and placed in the sample tube. For that, any asymmetrical pattern such as an arrow, would do. However, wanting to be most efficient, we decided to use the simplest such pattern, consisting of three points (or laser pits) with unequal distance between them, like a capital letter “L.”
SuperCam normally performs line scans (a single row) or grid patterns. To produce the “L” shape, we took a 2×2 grid pattern and removed one point from the sequence, so the laser only made three pits. Using 125 laser shots per pit, the result is shown in the image of the “Pinefield Gap” target. Sample cores are 13 mm (0.5”) in diameter, so the L patterns should fit well on their top surfaces. With the dry run successful, we are ready to use the procedure to mark future samples.
Over the last week, the Perseverance rover completed its second of two samples from Jezero crater’s delta formation, from the Skinner Ridge block at Hogwallow Flats. Over the weekend Perseverance drove about 25 meters to Wildcat Ridge, located slightly lower in Hogwallow, for more exploration.
Written by Roger Wiens, Principal Investigator, SuperCam / Co-Investigator, SHERLOC instrument at Purdue University