Space/Science — HabitableZone

Space/Science » in reply to "Bright Chunks At Phoenix Lander's Mars Site Must Have Been Ice."

Could rust or corrosion be the cause of the TEGA stuck doors?
Robert Clark — (archived)

I had thought that rust would have taken weeks to form but after a web search I found it can occur quite rapidly in the presence of salt:

Rust.
"When in contact with water and oxygen iron will rust. If salt is present, for example, in salt water, and the metal rusts more quickly. This chemical reaction is used in the production of handwarmers[2] Iron metal is relatively unaffected by pure water or by dry oxygen."
http://en.wikipedia.org/wiki/Rust#Chemical_reactions

Rust and rust prevention.
"If a weighed amount of iron filings is kept moist and exposed to the air for a week or two, then dried and weighed again, the mass of rust will be greater than the original mass of iron."
http://www.sciencetechnologyaction.com/lessons2.php?studyid=51

This page also says the reaction can be accelerated by carbonic acid, expected in a CO2 atmosphere with liquid water present.
However, the amounts of oxygen, usually required for rust, are quite low in Mars atmosphere so this might limit the rate at which this can occur. The "Rust and rust prevention" page only gives examples of rust occuring in anaerobic conditions when bacteria are present.
Another possibility is that it could be corrosion due to sulfuric acid, which is expected to exist with liquid water and sulfates present:

Why is sulfuric acid more corrosive to steel than hydrochloric acid?
http://wiki.answers.com/Q/Why_is_sulfuric_acid_more_corrosive_to_steel_than_hydrochloric_acid

Bob Clark

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