NASA's Perseverance Mars Rover

So that means all four sampling attempts made here on Witch Hazel Hill have been difficult in some way. Two of the attempts were outright failures, the last successful one only filled half the tube, and this latest one, #27, "overflowing" to the point of rendering the seal difficult.

I count four "difficult" sampling operations from the entire mission prior to reaching the Hill (Sample 1 an outright failure, Sample 15 difficult to seal as Mars Guy refers to in the video, and two outright failures on the delta fan around sol 810-813), maybe five if you count that problem with the pebbles getting stuck in the bit carousel after successfully snagging Sample 6.

It may have taken 37 sols, but they finally did seal Sample 15, so I'm not overly worried about this problem with Sample 27. What I find striking about all of this is the intersection of the geology with the engineering. The problem we encountered with the very first sample (the stuff simply crumbling and escaping the tube before we could seal it) was a warning shot to the rover operations team, but a fascinating sign to the geologists: this stuff has seen some serious alteration since it was originally laid down! And that weak, friable Sample 1 material saw much less transformation by water, mineralogically speaking, than Sample 27...

We knew that we were going to find igneous ("volcanic") geology combined with sedimentary geology (old river mud and sandstone) on this mission, but the intersection of the two giving us these kinds of problems is going to become part of the legend of Mars exploration. It may not be as controversial or unexpected as the Disappearing Methane Hunt or the Viking-era "biosignature" tease, but this sampling difficulty shows us just how tricky Mars is going to be.