The width of the OM image is about 1 mm. See <a...

The width of the OM image is about 1 mm. See this sol 17 OM composite of 3 frames for a scale.

Yes, I picked up on that siderite / biology connection -- which is why I suggested it as a possibility.

I would appreciate a reference to the OM specs too -- including the details of the substrates in the sample wheel. I am usually pretty good at locating this kind of stuff -- but the pdf google references for the OM were er, unresponsive. I think that was my first clue about how the OM was going to be treated in this mission.