This image is a close-up of the tailings (fine debris) left behind after Percy drilled for the latest successful sampling operation. The sharp contrast in colours seems to reveal a change found with increasing depth of drilling - the nearby abrasion patch, which is much shallower than the coring hole, mainly produced tailings of the duller, darker-toned kind seen surrounding the coring hole, as can be seen in this image comparing the two.

The row of small neat holes on the lighter-toned tailings (upper right) was created by the rover’s LIBS laser (the “death-ray” originally made famous by Curiosity), which is used when we want to know what kinds of elements (e.g. iron, magnesium, calcium) the target is made of. This laser analysis was done about four sols after the core sample was originally taken, just before the rover drove off to its next field site.

What will the elemental analysis tell us? For one thing, the science team will know quickly if the change in colours is caused by a sharp difference in composition, that is, if the rock is made of fundamentally different stuff as you drill deeper down. If that is the case, it would show that this old bedrock we’re driving over has more than one tale to tell about alteration, with different processes operating over just a few vertical centimetres near the surface. We already know from samples taken higher up the hill that this old crater rim has seen significant water activity… and yet earlier core samples didn’t produce these multi-coloured tailings, so something different was happening at this exact spot.

If the lighter-toned tailings have the same basic elemental make-up as the duller stuff, we still learn a lot - it means something other than a change in building blocks is responsible for that notable difference in colour. It’s worth noting that the ~35 prior drilling operations on this mission haven’t produced more than one shade of tailings… except in the case of the super-intriguing sample #25, from the Neretva Vallis channel. I expect we’ll be hearing a lot more about #25 in the next year or two - but as for the bedrock seen above in the latest one, #28, the scientists are pretty intrigued, given that they tried to get a second sample of this stuff, even before this latest laser analysis. Stay tuned!

EDITED to add context about earlier drilling operations.