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WCL (Wet Chemistry Lab) sample
pH of Martian Soils
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djellison
post Jun 26 2008, 07:50 PM
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Poll now closed, because that would be like...cheating smile.gif


Doug
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tedstryk
post Jun 26 2008, 07:54 PM
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QUOTE (Juramike @ Jun 26 2008, 07:48 PM) *
Nope. Not baking soda. That would hit a pH of 7 (neutral). More like sodium carbonate.


Baking soda has a pH of 8 or 9.


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Juramike
post Jun 26 2008, 08:04 PM
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QUOTE (tedstryk @ Jun 26 2008, 02:54 PM) *
Baking soda has a pH of 8 or 9.


I stand adjusted.

I made a basic error.

<ducks>


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ugordan
post Jun 26 2008, 08:05 PM
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QUOTE (Juramike @ Jun 26 2008, 10:04 PM) *
I made a basic error.

Lol.


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dburt
post Jun 26 2008, 08:20 PM
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QUOTE (TheChemist @ Jun 26 2008, 12:44 PM) *
High pH means that the salts involved have a "weak acid" part...
As Mike said, CO3-- (carbonates) or any other weak acid would be a good candidate...

May not be relevant here, but silica (SiO2) itself can be considered a weak acid, so that just freshly pulverized basalt (probably a major component of martian sand) will yield a mildly basic solution in contact with liquid water. You don't need a basic "salt" as such - any basaltic silicate mineral, olivine or pyroxene or plagioclase feldspar, will do.

-- HDP Don
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Airbag
post Jun 26 2008, 08:50 PM
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QUOTE (djellison @ Jun 26 2008, 02:50 PM) *
Poll now closed, because that would be like...cheating smile.gif


Doesn't matter much, since a pH of 8-9 was not one of the choices anyway smile.gif

Airbag
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TheChemist
post Jun 26 2008, 09:18 PM
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DOI: 10.1306/74D70E75-2B21-11D7-8648000102C1865D
Dissolved Products of Artificially Pulverized Silicate Minerals and Rocks: Part II
W. D. Keller, A. L. Reesman
Journal of Sedimentary Research
Volume 33 (1963)

ABSTRACT

Indeed, slightly basic pH (8.2 to 9.2) is reported by these authors for most silicate rocks.
More recent literature anyone ?

PS. It seems we were all biased by the "past acidic conditions" and the tons of sulfates at Meridiani :-)
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Juramike
post Jun 26 2008, 09:29 PM
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I was biased by the prospect of acidic windblown dust or salts making up the top layer of the surface.

I guess that didn't pan out.

<ducks and runs for cover>




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fredk
post Jun 26 2008, 09:39 PM
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QUOTE (TheChemist @ Jun 26 2008, 09:18 PM) *
It seems we were all biased by...

Except those of us who can barely remember from school which side of 7 is basic and which side is acidic, nevermind guessing what the conditions on Mars might be! tongue.gif

It may be worth stressing that at the briefing they pointed out that conditions may vary considerably with depth or with location on Mars. Today's result is likely just one data point rather than "the answer" to what the pH is on Mars.
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Cargo Cult
post Jun 26 2008, 10:31 PM
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Apparently we're all going to be eating asparagus on Mars.

Stinky urine, anyone?

Edit: that article has some ... interesting units. A cubic metre of soil? Blimey!
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djellison
post Jun 26 2008, 10:36 PM
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"The 1 cubic meter (35 cubic feet) of soil was taken from about 1 inch below the surface of Mars and had a pH, or alkaline, level of 8 or 9. "

Oh boy. Did they take the cartoon of Phoenix burying itself seriously ?

Doug
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Cargo Cult
post Jun 26 2008, 10:55 PM
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QUOTE (djellison @ Jun 27 2008, 12:36 AM) *
Oh boy. Did they take the cartoon of Phoenix burying itself seriously ?

Emily's blog is, as ever, far more informative - and suggests it was a cubic centimetre of soil sampled.

Oh well, Reuters was only out by six orders of magnitude. ;-)

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JRehling
post Jun 26 2008, 11:02 PM
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The free-style mixing of standard units and metric ought to be blacklisted in Mars exploration PR.

Some people -- you give 'em an inch, and they'll take a hectare.
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ngunn
post Jun 26 2008, 11:11 PM
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I agree. Non-metric has to go. It just acts as a fog.

I mean, Fahrenheit - for goodness sake spare us . . .

but save the pint! (no impact on science).
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BrianL
post Jun 26 2008, 11:47 PM
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QUOTE (ngunn @ Jun 26 2008, 06:11 PM) *
but save the pint! (no impact on science).


Well, save the Imperial pint. The US pint has got to go. biggrin.gif

Brian
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