MSL - SAM and CHEMIN, Discussion of the science/results from these instruments Options

[Astro0]

ADMIN NOTE: Hi All, a new topic for the discussion of the science from the SAM and Chemin instruments.
There has been a very important amendment to Rule 1.3 which is explained here.
Please remember Rule 1.3 at all times when discussing matters in this section.

[Don1]

The sample size is around 100mg so only 2mg of water would be produced. I don't think that would be feasible to collect.

The only thing that will work for MSL is a sampling strategy that collects organics while avoiding perchlorate. Since the perchlorate is falling out of the sky, a recently exposed surface at the base of a scarp may have less perchlorate than elsewhere. Another possibility would be to drill into the base of a cliff where an impermeable cap shields lower layers from perchlorate contamination. They'll just have to try different things, which is going to take time.

Another issue here is that the perchlorate is part of a bigger picture that may involve other oxidants. The oxygen from John Klein and Cumberland is being released at a lower temperature than at Rocknest, and the temperature of the release doesn't match that of common perchlorate salts. The presence of iron oxides may lower the decomposition temperature of perchlorate salts, or we may be dealing with a chlorate rather than a perchlorate.

For those who aren't familiar with chemistry, there is a family of these oxy-chlorine ions. Perchlorate has one chlorine bonded to 4 oxygens, while chlorate has one chlorine bonded to three oxygens. There is also chlorite with 2 oxygens, and hypochlorite with one oxygen. Household bleach is sodium hypochlorite solution.

For future reference here are links to charts showing SAM results from Cumberland, John Klein 4, John Klein and Rocknest.

[Gerald]

The sample size is around 100mg so only 2mg of water would be produced. I don't think that would be feasible to collect.

The cups aren't restricted to one sample (I don't know the upper limit). So heat e.g. 10 samples at once (1g) to get 20mg of water. (On Earth a drop is about 60mg.)
We're certainly dealing with a cocktail of several chlorine-bearing salts, and trapped oxygen, as perchlorates are decomposed via radiolysis, see e.g. this LPSC 2011 paper.

Techniques applicable to a sample to separate anorganic salts from organics, if water could be delivered to a cup, and if other methods fail:
- rudimentary fractional crystallisation on a microscopic scale,
- using previously heated samples as kind of chromatography column (stationary phase) with water as mobile phase. (More intuitive images here.) (Inspired by the electrophoresis idea of the Urey instrument.)

(Separation of organics from oxidizing salts would make them more likely to be detected.)

[stone]

There are several methods already developed.
*Alkohol extraction and than giving it through a cartridge filled with a unpolar substituted adsorbent and than wash it with hexane. (reversed phase solid phase extraction)
*HPLC is a method already very capable to work without the need to separate from most salts.

This all has a liquid extraction step and needs a lot of technical knowledge with no flight heritage. It will cost 80 million or more to develop. It will be 15kg+.

I would like to go for that but neither ExoMars nor 2020 will do such a thing.