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WCL (Wet Chemistry Lab) sample
pH of Martian Soils
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Juramike
post Jun 25 2008, 12:18 AM
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We'll soon know what kinds of crops we can grow on Mars! Bonus, the fruits will be already freeze-dried!

Handy list of preferred pH's of common garden plants.

-Mike


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CosmicRocker
post Jun 25 2008, 06:28 AM
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That's really a difficult question to answer, considering the actual Martian data that we have to work with.
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djellison
post Jun 25 2008, 09:38 AM
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'Don't know, it'll be interesting to find out'. Tick.



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Doc
post Jun 25 2008, 10:08 AM
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Considering the fact that there is water ice and some salt, basic minerals, I think we can make a rough assumption about the pH value of martian soil.
However the verdict is still open.


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tuvas
post Jun 25 2008, 01:49 PM
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My money is on fairly acidic.
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BrianL
post Jun 25 2008, 03:32 PM
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Oh man, my camp is dead last! The curse of the far side continues... sad.gif

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centsworth_II
post Jun 25 2008, 03:40 PM
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The results indicate that, as a group.... we don't have a clue! laugh.gif
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peter59
post Jun 25 2008, 08:44 PM
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The robotic arm has just delivered the first sample of soil to Wet Chemistry Laboratory.
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Cargo Cult
post Jun 25 2008, 09:02 PM
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The universe's first, interplanetary Pot Noodle?

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djellison
post Jun 26 2008, 05:52 PM
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Poll = Fail smile.gif

The results from the first sample are a pH between 8 and 9 smile.gif

Doug
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elakdawalla
post Jun 26 2008, 05:52 PM
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News: WCL analysis indicates pH of "8 or 9." Very surprising!

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tedstryk
post Jun 26 2008, 06:00 PM
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Someone spilled the baking soda....that explains all the bright patches Phoenix is seeing - Stu, you have your answer!


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Juramike
post Jun 26 2008, 06:48 PM
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QUOTE (tedstryk @ Jun 26 2008, 01:00 PM) *
Someone spilled the baking soda....that explains all the bright patches Phoenix is seeing - Stu, you have your answer!


Nope. Not baking soda. That would hit a pH of 7 (neutral). More like sodium carbonate.

Looks like we'll be sipping soothing mint tea on Mars...

-Mike

(P.S. my guess was at the other end of the pH scale)


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Bill Harris
post Jun 26 2008, 07:00 PM
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Not surprising. The pH is a rather quirky parameter that is also temperature dependent (although that may not be entirely relevant here). The WCL takes a sample of the regolith/soil and introduces it to water at an un-martian temperature. I get many hits to "phoenix pH WCL" and need to sort through them.

My first thought is that the high pH is from hydroxyl ions, but we'll need to see the entire chemistry to figure out what is happening.

Here is a quick-and-dirty explanation of pH _vs_ temperature:

http://www.lenntech.com/Correlation-betwee...Temperature.htm

which, again, may not be entirely relevant here.

--Bill


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TheChemist
post Jun 26 2008, 07:44 PM
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High -OH does not have to be present in the original sample.
A simplified view :
High pH means that the salts involved have a "weak acid" part, thus anions that form strong acids are probably low concentration in the sample:

Cl-, Br-, I-, SO4--, NO3-, ClO3-, ClO4-

As Mike said, CO3-- (carbonates) or any other weak acid would be a good candidate.

Remember this is a real sample, with many salts probably present so common ions effects might also be present.

Let's wait and hear what the Phoenix team's martian experts will say !

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