Blue Sky on Mars…

So this came up today based on something I just thought was a little weird, but as usual – Twitter makes the weird into something fascinating.

Let’s do a science, indeed!

The idea is this, and I’ll show a picture in a moment, on Mars – when the sun sets the sky and sun appear blue… not red as we’re used to. And here’s the proof – as photographed by the Spirit rover in… 2005 I think?

Okay, so it happens – oh, and I’ve got a video link you should watch later too – anyhow. It happens, and the WHY IT HAPPENS is the interesting part, because it has a lot to do with perception, wavelengths, and dust – and who doesn’t love that stuff, amiright? I am right.

On Earth when you look at a sunset, what you are seeing is light at a certain angle being scattered or absorbed – the light comes in at such an low that is must pass through lots more of our Earthy atmosphere, and as such – most of the blue and green wave-lengths (the short ones) of sunlight are scattered, – so our sky looks bluish, and the remaining  light of the sun appears to be a deep red  (the longer wavelength light that got to pass right through). And when we have more dust in our atmosphere – say from a volcano, or from living in Los Angeles – the effect is even greater.

Now… Mars has a very thin, very dusty atmosphere – and that dust is, like the rest of the planet, mostly red. So when the sun sets on Mars, the light passes through a thin atmosphere – which doesn’t scatter all the blue light because it’s thin remember, and then the light passes through this very fine red dust which reflects light of the same wavelength – the red light. The result being that the martian sky looks reddish, while the remaining light from the sun which reaches the surface is left looking very blue – and hence leaving us with the sight of a blue sunset.

And there you go – not too much of a science, but interesting all the same. The sunset on Mars is blue, because the dusty atmosphere is thin and red – and that means that most of the light that makes it through is blue. At least I think that’s about right… as always, it’s worth noting that I’m not a scientist and also you know how to google.

So… do a science and look up some more info on other planetary sunsets! Tell me what a sunset on Venus looks like, do a speculative science on the sunset of Saturn.

That’s kind of the awesome thing about this crap is that if you take what you do know and couple it with what the rest of the internet knows – you get to sound like you’re clever.

Have fun being nerds!

Oh, and here’s a video from the Opportunity rover looking at a blue sunset on Mars:

4 thoughts on “Blue Sky on Mars…

  1. RandomNerd says:

    Just a short question: Why are red wavelenghts supposed to be scattered more by red dust particles? If they [particles] are red, the blue wavelenghts get absorbed, which should make them be even less visible; also they are also more likely to hit a dust particle, since they are shorter? (Just my logic)

    • Oddly enough, and counter to first thought, red dust actually does the opposite of what you’re thinking – though I totally get your thinking. Good way to imagine it is if you had glasses on with red lenses – everything would look red – because the lenses absorb all the wavelengths aside from the red ones, which pass right through. Mars dust is sort of the same, it’s like layering the planet in rose coloured glasses.

      • RandomNerd says:

        Thanks for the fast answer; I know you are not a scientist and appreciate that you even care about… FUNDAMENTAL RULES OF THE UNIVERSE. 😀

        “if you had glasses on with red lenses – everything would look red – because the lenses absorb all the wavelengths aside from the red ones” … and therefore the sun should look red. I still don’t understand… :/

  2. joru says:

    my theory:
    when you look at sun, there is a bit of red from scattering, and white direclty from sun
    when you look at rest of sky, there is only red
    when you look at ground, it’s red, and lighted with redish light

    so sun isn’t realy blue, it’s white/red, but everything else is red, and your eyes compensate for red, so sun looks blue

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