Curiosity acquired this image using its Mars Hand Lens Imager (MAHLI), located on the turret at the end of the rover’s robotic arm, on July 6, 2024, Sol 4236 at 23:46:27 UTC.
The image features an after dark view of the Mammoth Lakes 2 drill fines and drill hole, it was taken from a standoff distance of about 10 centimeters (~4 inches) above the surface. For scale, the diameter of the drilled hole is 1.6 centimeters (0.63 inches)
Most images acquired by MAHLI in daylight use the sun as an illumination source. However, in some cases, MAHLI’s two groups of white light LEDs and one group of longwave ultraviolet (UV) LEDs might be used to illuminate targets. When Curiosity acquired this after sunset image, the camera group 1 white light LEDs were on, the group 2 white light LEDs were also on, and the ultraviolet (UV) LEDS were off.
Note the neat vertical array of ChemCam laser strikes on the side wall of the drilled hole. The laser is used to obtain spectra providing information about Chemical composition of the substrate of the drilled rock.
Image credit: NASA/JPL-Caltech/MSSS
Those are small pits made by laser shots from the ChemCam instrument. Each strike of the laser causes a tiny flash of light, that light is picked up by a telescope inside ChemCam and sent to three spectrographic analysers inside the rover. The data from the analysis can instantly record the chemistry of the rock (or sand) identifying its constituent elements and the percentages of each element present. The laser has been fired well over a million times at targets in Gale crater.
I think you’re referring to the five vertical spots running up the center of the far side of the hole, but I’m curious what these little dark flakes are:
OK, now I understand. They could be noise caused the lengthy night time exposure, or some dark inclusions in the host rock that was drilled. I’ll check to see if they appear in any other images, if so that will rule out noise, but if they are liberated inclusions from the rocks substrate, then we’ll likely never know what they are if the team decide not to investigate them.