When it comes to rocks from Mars, details matter a lot. NASA also plans to return small rock samples collected by the Perseverance rover to Earth for study. The aim is to understand where the samples came from in Jezero Crater and at the same time be able to trace the original orientations in the bedrock. For this purpose, the rover creates a small piece of physical graffiti on the Red Planet.
Perseverance used a laser, part of its pole-mounted SuperCam device, to mark three L-shaped dots on a rock in June. However, these marks are not used to create arbitrary graffiti and have valid scientific reasons.
SuperCam principal investigator Roger Wiens described the L as “the first letter engraved with a laser on Mars” in a mission update that went into detail about why the rover did this.
The rover is probing an ancient river delta that could give us the best chance of finding evidence of past microbial life on Mars. Therefore, the rock samples collected in this region are of particular importance.
Beyond the search for life, the brought back rocks could also help researchers reconstruct the history of Mars’ magnetic field and its effect on the planet’s atmosphere. The scientists studying it want to know the orientation of the rock fragments in order to understand the original direction of the magnetic fields in the samples. That’s why laser marking is used.
As Wiens points out, it’s easy to find the actual orientation of rock samples with easily recognizable features. But as he writes, “Only if the surface is fine-grained, there may be nothing to distinguish the direction of rotation. In that case we need to make artificial markings on the surface.” The fine-grained rocks of the river delta were the perfect place to test this method.
The team chose the capital letter L as a simple and effective way to make a signpost. “Once the dry run is successful, we are ready to use the procedure to mark future samples,” Wiens wrote.
The rover could use its typing skills to engrave all sorts of messages into Martian rocks, but NASA is more interested in using the wheeled lab’s energies for science rather than fun.
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