Washington People: Bill McKinnon

Our knowledge of the solar system has exploded since Sputnik went up in 1957. How much was known when you were young?

When I was a boy, we hardly knew anything. What we knew would fit between the covers of a “How and Why Wonder Book of Planets” or, in my case, a book in the “Exploring” series by writer Roy Gallant. We knew how many planets there were and how big they were and that they had moons, but it was all very mysterious. I really wanted to find out about them.

Did they know how many moons Jupiter had, or Saturn?

Well, astronomers discovered the big moons early on. Then, one by one, smaller moons would be picked up by telescopes. And we keep finding new ones. Let’s consult the oracle. . . the font of all knowledge. . . the Wikipedia.


We’re up to 67.

Good grief.

My thesis was on the physics of impact craters, the ones on our moon and, to some extent, Mars and Mercury. But the Voyager missions were launched while I was in graduate school. I had a postdoctoral research appointment with one of the Voyager imaging team scientists when the spacecraft reached the icy moons of Jupiter in 1979, and we saw them for the first time.

So then I decided that instead of studying impact craters in rock, I’d study impact craters in ice.

But then the bodies themselves became interesting. The Voyagers reached Saturn in 1980 and 1981, and Voyager 2 went on to Uranus in 1986 and Neptune in 1989. So it was a moveable feast.

The sheer strangeness of these places, which became real worlds once we could see them, was fascinating to me. So I left the inner worlds of the moon and Mars behind.

There’s more people working on Mars than on any other solar system body. It’s just like being on the Earth, these days. And somebody has to pay attention to stuff beyond the ice line.


I’m teasing.

The ice line?

The line that marks the border of the region far enough from the sun that water ice remains stable on a planet or satellite’s surface. 

Read more at The Source. 

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