Monday, July 20, 2015

Whatever happened to Pluto's craters?

Or ... a funny thing happened on the way to the Kuiper Belt.

I wrote my last article about Pluto in a flurry of excitement after we received the confirmation that New Horizons had made it past Pluto, and had captured data.  There was just a minor problem, to "do the science", the probe had to turn it's camera toward Pluto, and hence it's dish away from the Earth, and so it's only much after the event that we're starting to see some of the more closer images.

Even so, the latest images we'd had before it "went silent for science" he had back were pretty exciting.  I also said looking at them, "We see craters on Pluto, but not many of them".

In my last article, I talked about the planetary evolution science I learned in my degree.  We formed from a cloud of dust, it collides to make bigger and bigger objects (the Sun, it's planets and their satellites).  It's a somewhat chaotic process - eventually the planets form, but there's still asteroids and comets out there still colliding with them.  That can range from a fairly minor event (shooting star) to something more catastrophic (move over dinosaurs).

These impacts are most dramatically seen on the Moon and Mercury - because these world have no weather system, so remain preserved ...

We see craters on Venus, the Earth and Mars - but in each case the weather can erode these over time.  We also see them on many of the satellites of the ice giant planets, one of the most dramatic of which is Mimas, which has a giant crater which makes it look a little like the Death Star.  In actual fact we don't think you could have a bigger crater without the satellite splitting!

So we know that cratering happens throughout the universe - so look at that picture of Pluto.  Can you see those dark marks, especially the spots, which have to be craters?  Can you see the craters there?

There's just a problem which occured the day after I posted, and NASA scientist started posting, how one of the few things they haven't seen is any craters on Pluto.  But yet huge mountain ranges on such a small planet.  With so few craters out there either Pluto is relatively young, or something odd is going on out in the Kuiper belt, with incidents of cratering so incredibly low compared to elsewhere in the solar system.

So I got it wrong.  But what's been really interesting to me, is how I got it wrong.  It's a fantastic demonstration of an effect called confirmation bias, which I was always hoping to find a way to cover, and here we are!

First of all - I need you to be honest.  When I talked above about seeing dark rings in picture of Pluto, did you see craters too?

Confirmation bias works like this - if you look at a picture like that, which is slightly fuzzy, if you know that craters exist all throughout the solar system.  Then you are going to see shapes which your mind will recognise as craters.  Your mind is looking to confirm what it already thinks is there.  The problem is, there are no craters there, you've created a mirage of geology in your mind, you've fooled yourself.  And this in many ways is how much magic and illusion works.

It's a huge problem for us, because our eyes will sometimes see what our mind and heart really wants to see.  And this can be a problem for everyone, even scientists and testers.  How many times have you found a bug, and tried a few different options, and sure you know what the pattern is, then someone tries something around your patten, and shows a huge hole in it?  This is how it impacts us.

I'm going to talk a bit more about this in my next piece, focusing on how this impacts us in testing.  But for now I'll leave you with a picture of the Sputnik plain on Pluto, more "not craters" ...

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