I'm looking at this graph:

and I'm thinking...okay, the data could suggest a relative increase in bromine verses chlorine in the Meridiani samples: OR it could suggest a depletion of chlorine. Add chlorine to these samples and they start to cluster near seawater. A curious thing I've recalled about chlorine from my College lifeguarding daze, a bright sunny day can really deplete the chlorine from pool water. Something about the UV rays drives it out of the water. What causes the change in the ratio in earth evaporites? I don't know, yet. What is the difference between the Dead Sea evaporites and martian evaporites? (aside from the obvious) More UV on mars, for one.

But, in the graph of Cl vs. SO3, the brushed surface (ie, the blue-gray rind) is relatively enriched in chlorine.

Maybe on it's way out of the rock? Or into it from the atmosphere? Or a product of mineral alteration? Most likely the last one but which mineral? What mineral contains the Cl? Apatite? Chlorapatite? (just learned that the name Apatite comes from a Greek word, which means "I am misleading." pretty funny) Still thinking on it. Need to see the brushed surface plotted on the first graph, see what it is doing relative to bromine. I'm still thinking about how this graph fits in with Nick's thoughts on a meterorite surface glass. Would that be enriched in Cl and SO3? What's clear, is that the deeper you go into these rocks, the less Cl and SO3 you encounter. So it is probably (?) a weathering rind, but under what conditions, what are the reactions?

~~~~~~~~~~~~~~

What I'm reading to answer my own questions:

The downloadable files list from the 2004, 35th annual Lunar and Planetary Science Conference was updated since last I looked (some time ago). There's lots of good reading here, I've only just begun to dive into it.

The session that most caught my eye, given my current geologic curiosity was this,
Weird Martian Minerals ( 3-18-2004, poster session abstracts, 2.7 megs). It's a rainy day, I'll waste some time reading this, see what it has to say about Cl.

~~~~~~~
Here's some other reading:
Mars brine experiment. An effort to reproduce brines to model the process on Mars.

CAN LOW WATER/ROCK HYDROTHERMAL ALTERATION OF IMPACT MATERIALS EXPLAIN THE ROCK COMPONENT OF THE MARTIAN SOIL?

THE COMPOSITION OF THE MARTIAN HIGHLANDS AS A FACTOR OF THEIR EFFECTIVE UPLIFTING, DESTRUCTION AND PRODUCTION OF VOLUMINOUS DEBRIS.

Enjoy your day...