Why is Mars Red?

Oddly enough, I sometimes get questions tweeted to me – for which 140 characters just can’t manage to answer. So, on those rare occasions when this happens – I’ll write about them here and try to answer them better.

Let me also say that I am by no means a scientist of any account, but I do want to put on a good face for science in general, and to at least not “let down the side” as it were when it comes to NASA, the MSL, or Curiosity – none of whom are at all affiliated with me.

So here’s an interesting question I got asked today:

@fire_n_air wrote to say:

Hey @SarcasticRover If rocks r red on Mars coz theyre rusty but theres no oxygen, how did they rust? Do a science and find out? #fistbump

This is a very good question – and like many good questions, the answer is… No one really knows.

The fact is that the rocks on Mars ARE red due to rust, being mostly comprised of iron – but precisely how they came to be rusty is a matter of some debate. However, three theories stand as the most likely and/or interesting.

1) A bajillion f–king years and nothing else to do.

This theory basically holds that, while there is very little oxygen and water in the atmosphere of Mars – if you give what little there is enough time to work, then those rocks are going to rust, no matter what. Rusting rocks are essentially a chemical and geological process and if you give those sorts of things a chance and some time – they’ll get done. The sun’s rays break down the water in the atmosphere and oxidation occurs in the minute amounts of oxygen released in the process.

2) Water + Iron = Dirty Red Stupid Planet.

The second theory ties very much into the first – except that it adds the presence of liquid water in Mars’ past to act as a catalyst and really speed up the whole game. Geological evidence shows that, like Earth, Mars was once a hotter – more welcome place to liquid water, and that water could have begum the oxidation of the planet’s iron surface – resulting in the monochromatic Mars we know today.

And lastly we have…

3) Albert Yen F–ks it All Up.

Back during the Pathfinder mission, the craft found evidence that there was more iron in the soil of Mars than the rocks – which was odd, and may point to the addition of meteorites depositing some of the iron on the planet. This concept led Dr. Albert Yen of JPL to put forth a new theory – that the oxidation of the Martian surface didn’t require any liquid water at all. Basically, Dr. Yen’s theory involves ultra-violet light reacting with certain Martian minerals (in this case labradorite) to produce negatively charged oxygen particles which react with the iron and oxidize it without the need for any water at all. The theory is interesting, but also has the worrying side-effect of requiring more time than the solar-system has been in existence… so water and time still seem to be our best bet.

BUT… the original question raises an interesting point. There may be very little oxygen on Mars, but let’s not forget that when iron rusts, the iron combines with oxygen to form IRON-OXIDE… the rust that we know. So perhaps we shouldn’t think of Mars as not having oxygen, but instead consider the idea the what oxygen is there, has been locked up inside the rocks – coating the planet, perhaps waiting for us to find some way of getting back out into the atmosphere.

But now I’m just spit-balling and I am basically an idiot with a laptop.

3 thoughts on “Why is Mars Red?

  1. Matt Phillips says:

    Hey SarcasticRover you are awesome, please keep the tweets coming. And you actually know things about doing sciences! I had no idea.

  2. B. Nelson says:

    Meanwhile….
    over at WUnderground:

    996. Angela Fritz, Atmospheric Scientist (Admin)
    11:27 PM EDT on August 14, 2012 +6

    …………………
    Quoting CaicosRetiredSailor:
    Aha….
    I saw Angela fraternizing with a Martian:

    SarcasticRover
    @SarcasticRover
    I appreciate NASA trying to cover all bases, but I can’t imagine under what circumstances I’ll ever use these Encarta CDs.
    1 hour ago via Twitter for Mac

    Angela Fritz
    @angelafritz
    @SarcasticRover I LOVED Encarta! …In 1996.
    44 minutes ago via Twitter for iPhone

    : )
    …………………

    That rover is a cute little guy. Im a sucker for science.
    Action: Quote
    ==========================================

  3. @SarcasticRover: That is a lucid, intelligent, well thought-out explanation… however, I believe the iron oxygen bonds are very strong and you will have a hard time getting free oxygen from the iron oxide in the rocks. Not to be too pessimistic, but I hope you can hold your breath for a while.

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