I should make this brief.
I don't believe that 'premature speculation' is wrong.
If it were, then HZ Space forum, would be little more
than a regurgitation of what's already news elesewhere.

Yes! I believe that any discovery of a mixed layer
of Olivine and Hematite on Mars would be difficult to explain
if you stick to the orthodox scientific interpretation that the last volcanic eruptions on Mars, and the last large bodies of water, occurred millions and billions of years ago.

But kick in some free-speculation, using Occam's Razor as a guide,
and wouldn't it be possible that BOTH some limited volcanic eruptions and some small bodies of ice-covered water occurred as RECENTLY
as a few hundred-thousand, or a few thousand years ago? A
And wouldn't that ADEQUATELY explain a possible mix of Olivine and Hematite in Opportunity's vicinity?

I don't think either premature or free-speculation are wrong.

Jacob