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First drill stop: John Klein in Yellowknife Bay, Site 6, Sol 166-271, January 23-May 12, 2013
Guest_Actionman_*
post Mar 20 2013, 05:03 PM
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"it's a little complicated" pancam.gif
Just so me a layman can understand what mite be being said, the presence of perchlorate is using a catalyst that is taking some carbon atoms from an indigenous organic to produce the recorded chloromethane ... if the second test is affirmative for the same levels found in the first test of the powder.
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Julius
post Mar 20 2013, 05:43 PM
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I hope I'm getting this right but being a layman in geology I have to make an extra effort to understand whats being said and what it means.. before Curiosity rover, I had the impression that sulphate rock as typified by rocks found at the Meridiani site was a rock type completely separate from the phyllosilicate detected from orbit at the Endeavour crater rim site. We were told this probably signified a transition in climate from a neutral Mars to a more acidic environment as Mars was drying up. Now that we have analysed the rock site at YB by Curiosity, does it look like sulphate and phyllosilicate are to be found within the same rock and if that is so, how would one explain that??
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Paolo
post Mar 20 2013, 06:36 PM
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in today's Nature: Mars rover under pressure to reach mountain goal
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stone
post Mar 20 2013, 08:39 PM
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QUOTE (Actionman @ Mar 20 2013, 06:03 PM) *
"it's a little complicated" pancam.gif
Just so me a layman can understand what mite be being said, the presence of perchlorate is using a catalyst that is taking some carbon atoms from an indigenous organic to produce the recorded chloromethane ... if the second test is affirmative for the same levels found in the first test of the powder.

A soil sample is put into the oven it is heated with 35°C per minute. The Mass Spectrometer looks what is coming off at each temperature in a small amount of the gas.(This is evolved gas analysis EGA) The rest of the gas is going into a cold trap and is stored there until the 850°C in the oven are reached and the run is over. This trapped material is mobilized by heating and injected onto one of the six columns of the Gas Chromatograph. The GC separates the compounds and the faster ones coming of early while the ones which have more interaction with the column material take longer. All the gas coming from the column is analysed by the GC.

The first analysis of rocknest and john klein showed in the EGA a lot of oxygen and a lot of carbondioxide. Oxygen is generated by oxygen rich substances like chlorate perchlorate nitrite or nitrate. ==> Perchlorates are present (perchlorates were shown to exist on Mars by Phoenix)


The GC analysis showed that there are monochloromethane, dichloromethane (methylenchloride) and trichloromethane (chloroform) present together with breakdown products of a substance used in still sealed ovens for the derivatization of organic molecules. ==> There is a leak of derivatization reagent!
Organic material heated together with perchlorates give mostly carbondioxide. The reaction is very similar to the reaction in a shuttle buster. Small amounts react to form the chloromethanes mentioned above.==> You have now no chance to find out where the carbon atoms in the chloromethanes come from. Martian organics yield carbondioxide and chloromethanes. Meteoritic organics yield carbondioxide and chloromethanes. Small forms of life yield carbondioxide and chloromethanes. Derivatization reagents yield carbondioxide and chloromethanes.



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serpens
post Mar 20 2013, 10:33 PM
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QUOTE (Julius @ Mar 20 2013, 06:43 PM) *
..... We were told this probably signified a transition in climate from a neutral Mars to a more acidic environment as Mars was drying up. Now that we have analysed the rock site at YB by Curiosity, does it look like sulphate and phyllosilicate are to be found within the same rock and if that is so, how would one explain that??

At an arm waving level it is really quite simple Julius and there is no contradiction. The clays of interest are smectites which indicate non acidic water whereas other clays like kaolinite can actually form in acidic conditions. Mars is basaltic so groundwater (and probably surface water prior to the acidic period) would be buffered (non-acidic). During the volcanic driven sulphate period the surface would have been acidic. Smectites have a great capacity to consume acidy and the lower the pH the greater the rate of dissolution with the end product being amorphous silica. So with surface acidity and buffered groundwater a top down transformation would be expected. This top down alteration scenario seems to be substantiate by Mawrth Vallis where there is a layer of mainly nontronite (Fe rich smectite) overlain by a more resistant to acid leaching Al-phyllosilicates unit (montmorillonite) mixed with hydrated silica. Above that is kaolinite plus hydrated silica.

So clay and sulphates together is possible, even smectites and sulphates if there was a rapid drying out or recharge of buffered groundwater.
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Julius
post Mar 21 2013, 05:28 AM
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Thanks it sounds like a plausible scenario...on another theme, dont know why they only mention D/H isotope ratio of water which I understand it relates to the age of the rocks but no mention so far of isotopic ratios of sulphur and carbon!
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marsophile
post Mar 21 2013, 05:38 AM
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QUOTE (stone @ Mar 20 2013, 01:39 PM) *
You have now no chance to find out where the carbon atoms in the chloromethanes come from.


If you have the C12, C13, and C14 ratios (as just suggested above), doesn't that give some hints as to where the carbon is coming from?
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stone
post Mar 21 2013, 07:27 AM
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I think you only get the isotope ratios from the Tunable Laser Spectrometer for methane and carbondioxide. The chloromethanes are most likely not in the range for the TLS, but this is only a guess. The MS is not giving you good values, because it was not built to do this and the chlorine has two isotopes which interfere with the others.

To have a good clue where the carbon source is you have to know the carbon isotope ratio of the source. For meteoritic source and the derivatization agent this might be easier than for the isotope ratio of Martian organic carbon. The carbonates on Mars are a large source for carbondioxide in the measurments by SAM and there is no data for the isotope ratio of those carbonates. Good isotope measurement results will be presented at the end of the mission when you can plot all the data Curiosity ever measured in one plot. With nobody ever done this and two points in the plot it is hard to tell a good story.
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jmknapp
post Mar 21 2013, 09:40 AM
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QUOTE (stone @ Mar 20 2013, 03:39 PM) *
Perchlorates are present (perchlorates were shown to exist on Mars by Phoenix)


I suppose it's an important data point that they found them here too. Didn't some theories have them unique to the polar regions?


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stone
post Mar 21 2013, 11:09 AM
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Catling published a paper about this in 2010

The Viking GC-MS data suggests them too.

The production of perchlorate in earth atmosphere is well established and this happens by radical reactions of oxygen or hydroxyl radicals with salt (sodium chloride). The salt can be placed in that heights by volcanic eruptions or ...

For the radicals UV is needed, on Mars the UV penetrates deeper into the atmosphere so there is the theory that it is formed on the dust on the ground or formed like here on earth in the upper atmosphere. All you need is sodium chloride and this is most likely distributed all over Mars. If the dust is the carrier it is everywhere.

One point is: Was it there during the wet period or did it form later?

http://faculty.washington.edu/dcatling/Cat...Perchlorate.pdf
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jmknapp
post Mar 21 2013, 12:55 PM
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QUOTE (stone @ Mar 21 2013, 06:09 AM) *
or... For the radicals UV is needed, on Mars the UV penetrates deeper into the atmosphere so there is the theory that it is formed on the dust on the ground.


Here's the paper I was thinking of:

Photooxidation of chloride by oxide minerals: implications for perchlorate on Mars.

You can get the first page of it at that link. The authors say that certain characteristics of the Phoenix perchlorates are difficult to explain using analogies from Earth processes. They posit that the perchlorate could have been formed on the surface by UV irradiation of naturally occurring semiconductors (now that's cool), but requiring an aqueous solution as an electrolyte.

QUOTE
The thin Martian atmosphere, with low ozone levels, allows more solar UV radiation to impinge on the surface of Mars than on Earth, making heterogeneous reactions on mineral surfaces particularly relevant during carbon dioxide ice-free periods in Martian polar regions when condensed liquid water eutectics containing chloride and other salts could undergo photochemical reactions. The periodic wetting of the soil during Martian seasonal ice cap thawing and melting cycles, where initially a chloride containing eutectic electrolyte was present, could eventually oxidize nearly all available chloride ion especially as the freezing point was lowered by the accumulation of perchlorate.


But if perchlorates are everywhere (extrapolating from the standard engineering sample size of two smile.gif) including this dry dry place, I wonder if it might tend to discount this theory.

BTW, if the robotic arm was tested a sol or two ago, there haven't been any new images, and NAIF data files haven't been updated.


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Guest_Actionman_*
post Mar 21 2013, 03:06 PM
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Spaghetti Density Determination Technique
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Eutectic
post Mar 21 2013, 05:42 PM
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QUOTE (stone @ Mar 21 2013, 02:27 AM) *
The carbonates on Mars are a large source for carbondioxide in the measurments by SAM and there is no data for the isotope ratio of those carbonates...


There is at least a little information on carbon isotope ratios from the Martian meteorite ALH84001, as quoted below. Of course, nobody knows how representative ALH84001 is of Martian carbonates in general.

http://www.sciencedirect.com/science/artic...016703705000074
QUOTE
Microscale carbon isotope analyses of ALH84001 carbonates reveal variable δ13C values ranging from +27 to +64‰. The isotopic compositions are correlated with chemical composition and extent of crystallization such that the Mg-poor, early-formed carbonates are relatively 13C depleted and the Mg-rich, later forming carbonates, are 13C enriched.
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PaulH51
post Mar 21 2013, 09:57 PM
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QUOTE (jmknapp @ Mar 21 2013, 08:55 PM) *
...BTW, if the robotic arm was tested a sol or two ago, there haven't been any new images...

Good news indeed, hope to see some new images soon so that we have something to review during solar conjunction smile.gif
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jmknapp
post Mar 22 2013, 10:31 AM
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I don't know about good news--the key word is "if." A HAZCAM engineering shot would be reassuring.

As for images for science sake, maybe they've already covered this locale to a fare-thee-well? I think they said they don't want to drill again until after spring break.


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