Bizarre Astronomy: Canals on Mars

23 April 2019

Interview with 

Beth Biller, University of Edinburgh

MARS-DUST-STORM

Image of Mars during a dust storm

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Beth Biller from Edinburgh's Institute of Astronomy tells Adam Murphy about the martian mistake that caused a lot of confusion amongst astronomers...

Beth - This is a bit of a historical one and one that they didn't actually see, which is canals on Mars. For a period of time in the late 19th century and early 20th century there was this idea that there are these canals on Mars and that they were the result of a civilization trying to save themselves from their dying, drying planet, transporting water from the polar caps down to the mid-latitudes, and this was completely false. I think it's 1879, Giovanni Schiaparelli was looking through a fairly small telescope looking at Mars and started drawing all these lines. And after that a number of other astronomers started claiming that they saw these lines, notably Percival Lowell who started Lowell Observatory in Arizona in the United States. And there are all these different maps of all these very complicated canal systems.

Now one thing that might have been an indicator that this was maybe not a real feature on Mars is that everyone drew a rather different set of canals. These paths didn't agree with each other at all. It's an optical illusion or rather I think it's it's your brain filling in details where they're not. In this case these are people who are looking through fairly small telescopes, not photographing things, and the reason they weren't photographing things is because the atmosphere is really turbulent. As you're looking through a telescope sometimes you're going to be looking through slightly more turbulent parts of the atmosphere, sometimes you're going to get a less turbulent cell. And when you get that lucky less turbulent cell, then you can see your surface features on your planet much more clearly. And essentially these people were waiting for those moments, saying “Oh look at all these lines we see, draw them really quickly”. And it really is just your brain filling in details. With better telescopes all of these features went away.

Adam - I know it's probably quite serious, but I'm picturing Martian gondola drivers, going down these canals.

Beth - Absolutely, there is so much science fiction that was written up until the mid 20th century with exactly these ideas. I mean Percival Lowell went on and started drawing similar line shapes on Venus as well. Who's been to the eye doctor and had them shine a light in your eye and then you see all the lovely veins on your retina. Most people are nodding. Venus is really bright, right, even through a small telescope, Venus is really bright and if you stop down your aperture you're putting a lot of light through your eye at once. It's thought that maybe some of the spoke patterns that Percival Lowell saw on Venus were him drawing the structure of his own retina. But it's a cautionary tale because with astronomy we have to be careful to test what you see and to make sure it's actually there, so you're not creating wishful thinking structures.

Adam - So we don't think there are canals now?

Beth - We don't think there's canals. There's not a face or pyramids either on Mars.

Chris S - You'll be telling me the moon's not made of cheese, next.

Beth - I have some disappointing news for you.

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