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NASA’s Mars Perseverance Rover: Laser Marking on Mars

Apr 25, 2023

By Roger Wiens, Purdue UniversityAugust 4, 2022

Illustration of the Mars Perseverance Rover using its SuperCam instrument to laser zap a rock in order to test what it's made of. Credit: NASA

If your name begins with "L" you will especially enjoy this story about the first letter to be laser engraved on MarsMars is the second smallest planet in our solar system and the fourth planet from the sun. It is a dusty, cold, desert world with a very thin atmosphere. Iron oxide is prevalent in Mars' surface resulting in its reddish color and its nickname "The Red Planet." Mars' name comes from the Roman god of war." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">Mars.

Every once in a while, we see cartoons where a Mars rover is driven in a pattern to make letters in the sand with its wheel tracks. The letters may spell out a silly phrase, and the cartoons often have aliens on the side, laughing or puzzling over the meaning. In real life, the use of lasers on board Mars rovers has also made it possible to laser-mark graffiti on Martian rocks.

However, as NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">NASA's instruments are generally used strictly for science, I did not believe laser graffiti would ever be done. But of course, people have thought about it. When I arrived at JPLThe Jet Propulsion Laboratory (JPL) is a federally funded research and development center that was established in 1936. It is owned by NASA and managed by the California Institute of Technology (Caltech). The laboratory's primary function is the construction and operation of planetary robotic spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA's Deep Space Network. JPL implements programs in planetary exploration, Earth science, space-based astronomy and technology development, while applying its capabilities to technical and scientific problems of national significance." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">JPL for the landing of Curiosity in 2012, I was surprised to find that one of our engineers in charge of developing sequences for 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 (MITMIT is an acronym for the Massachusetts Institute of Technology. It is a prestigious private research university in Cambridge, Massachusetts that was founded in 1861. It is organized into five Schools: architecture and planning; engineering; humanities, arts, and social sciences; management; and science. MIT's impact includes many scientific breakthroughs and technological advances. Their stated goal is to make a better world through education, research, and innovation." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">MIT) asking about SuperCam's laser marking capabilities. Ben had just joined Perseverance as part of the Return Sample Science team. This group focuses on the collection of samples for return to Earth, with the purpose of ensuring that samples would be collected under the appropriate conditions to optimize their scientific value once back on Earth. Ben's specialty is paleomagnetism. In terrestrial rocks, this is the study of the magnetism induced by the Earth's magnetic field at the time of the rock's formation. Mars currently has a very weak magnetic field, but Mars’ field strength in the past is largely unknown. It has important implications for the retention or loss of Mars’ atmosphere over time, among other things. Suffice it to say that we would love to use the samples returned from the Perseverance mission to fill in that knowledge gap.

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