[X] My Assistant

[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.

[marsophile]

For some context, we had the following results from the Viking GCMS.
Sample T Compound Abundance (ppb)
VL1
Blank Test 500 CH3Cl Not Detected
Sample 1 200 CH3Cl 15
VL-2
Blank Test 500 CH2Cl2 Not Detected
Sample1 500 CH2Cl2 2-6
Sample2 500 CH2Cl2 20-40

For a discussion, see this paper:
http://www.agu.org/pubs/crossref/2010/2010JE003599.shtml

The original Viking GCMS results were published in this Ph.D. thesis:
http://dspace.mit.edu/bitstream/handle/172...69/07517313.pdf

See for example, Pages 203 and 204 for VL-1 and VL-2 chlorinated hydrocarbon results.
(Methyl Chloride = Chloromethane, Methylene Chloride = Dichloromethane)
Also chlorinated hydrocarbon results from Antarctic soils Pp 233,242,250,258.

[marsophile]

Also chlorinated hydrocarbon results from Antarctic soils Pp 233,242,250,258.

What I find fascinating is that chloromethanes were detected by tests of the Viking GCMS in Antarctic soils.

Apparently these soils do also contain perchlorate:
http://pubs.acs.org/doi/abs/10.1021/es9033606

If this hint had been followed up, we might have hypothesized the presence of perchlorate in Martian soils a lot earlier.

[dvandorn]

...If this hint had been followed up, we might have hypothesized the presence of perchlorate in Martian soils a lot earlier.

Well... perchlorate was one of the options that was being discussed at the time of the original GCMS experiments on Viking. The phrasing I recall is that the time-release experiment data fit well with a Martian soil rich in "super-oxidants," and one of the super-oxidants that headed the list was perchlorate. I believe the presence of chlorine in some of the evolved gasses seen in the Viking results is what led to that speculation, 36 years ago.

I don't have any articles of the time in front of me, but I am very confident of my memory of the "super-oxidant" reports.

-the other Doug

[mcaplinger]

Well... perchlorate was one of the options that was being discussed at the time of the original GCMS experiments on Viking. The phrasing I recall is that the time-release experiment data fit well with a Martian soil rich in "super-oxidants," and one of the super-oxidants that headed the list was perchlorate.

I don't think so. At the time H2O2 or superoxides were used as explanations for the O2 release seen after wetting in the GEx experiment, and CO2 release in the LR experiment. I'm no chemist but I don't think perchlorates alone explain these results; see http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2003.pdf for example. And I don't think that perchlorates are technically superoxides.

I'd be happy to be proved wrong but it would take an actual reference from pre-Phoenix to convince me that anyone had mentioned perchlorates in the context of Viking.