Life on Mars - Ferric Oxides?

[Thunder Chicken]

I read in Bill Bryson's A Brief History of Everything that when photosynthesizing microbes first came to being on Earth, much of the liberated oxygen went into oxidizing iron in rocks and soils, producing the red iron ore.

Admittedly Bill Bryson is not a scientist and there were many errors in transcription in that book, but it is a fair question - wouldn't the abundance of these ferric oxides on Mars suggest a similar oxygen producing life form acting there at some point? Are there alternative non-biological oxidation mechanisms that can account for this?

 

[Eagle]

Gases from Volcanoes and plain old water can provide the needed oxidation.

EDIT: I don't really find the color as extraordinary as others do. Where I live the dirt ranges from blood red to dull orange. I think the clay gets its color from the Anorthosite which has several iron oxides mixed in.

 

[Belisarius]

Ultraviolet radiation is thought to be responsible for the red colour (I'm looking for the reference - can't find it yet)

 

[mrspacely]

could the red tint come from a massive destructive event that scoured material all over the planet?

 

[Thunder Chicken]

I guess I need a brush-up on chemistry. If I were to throw an iron bar into a container of pure water (assume no dissolved O2 or other gases, just water). Would we get iron oxides and hydrogen gas? Something is amiss with the electrochemistry if my memory serves - don't we need some electrons somewhere? If this were the case, couldn't we make a battery with iron and water?

Thanks for your comments (and to whomever gave this thread 5 stars!?!)

 

[thomasantony]

I guess I need a brush-up on chemistry. If I were to throw an iron bar into a container of pure water (assume no dissolved O2 or other gases, just water). Would we get iron oxides and hydrogen gas? Something is amiss with the electrochemistry if my memory serves - don't we need some electrons somewhere? If this were the case, couldn't we make a battery with iron and water?

Thanks for your comments (and to whomever gave this thread 5 stars!?!)

Well actually, if you put the iron bar in pure distilled water, I think it will rust only if a part of it is exposed to air. This differential aeration creates a potential difference or a kind of battery and electrons flows from the part under water to the part above, rusting the submerged part.

http://en.wikipedia.org/wiki/Galvanic_corrosion
http://en.wikipedia.org/wiki/Cathodic_protection

~
Thomas

 

[Thunder Chicken]

I think the last line of the Wiki page is helpful:

Even a single type of metal may corrode galvanically if the electrolyte varies in composition, forming a concentration cell.

Assuming Mars had no biogenic oxygen, just having iron-laden rocks in a salty sea (with variable concentration) would be enough to get electrons where they needed to be. The rocks take the oxygen from the water, and the hydrogen evaporates.

This leads to another question. The gravity of mars is not enough to hold onto hydrogen, the thin atmosphere is mostly CO2. Could mars hold onto a significant water vapor atmosphere? If there were seas on mars, how could they amass and how long would it take for them to boil away?