This text is from JPL's social media post...
Have you ever found an old book and blown the dust off to see what story it might have to tell? That’s pretty much what I’m doing here. I came upon an interesting boulder, hit it with a puff of compressed air, and am taking a closer look. I’ll see if I can get a peek inside, too.
When this image first came down I thought it looked as if someone had taken a pencil and scribbled on the side of this large rock. This is a much more plausible explanation I think.
They have since abraided the rock on top of the site where they used the gDRT. After abrasion they will normally examine examine the fresh surface with PIXL and SuperCam. The results from those investigations will determine if they take a core sample, or move onto the next science waypoint.