Exposing PseudoAstronomy

June 16, 2012

Podcast Episode 40: Crater Age Dating Explained, Part 1

This is a bit of a longer episode. ‘Cause, this is what I do.

I give you a pretty detailed overview of how crater age dating works, the difference between absolute and relative age dating, how we can assign absolute ages to the relative ages of craters, how geologic mapping works and why it’s important for crater age dating, and then many of the known problems and caveats with the method.

Finally, there’s an open question about the puzzler: Is it worth doing? I wanted to do it initially to get interaction between me and the listeners. But participation has been around 1 for each. So if you have any opinion regarding the Puzzler, please let me know in the Comments to this post.



  1. Is there statistical information about the angle at which incoming rocks have struck, say, the Moon to create craters? Commonsense would suggest that a perfect 90° would be a rare event, and yet most craters seem to be perfectly circular or nearly so.

    I guess another way of asking this is, can an oblique impact create a circular crater and if so how?

    Comment by Expat — June 19, 2012 @ 8:25 am | Reply

    • Indeed, there is, and I’m on two published papers about this. The average angle is 45 degrees. You don’t start to get obviously elliptical craters until the impact angle is well below about 10 degrees, though this also varies by diameter according to some new models. I’ll use this in Q&A in the next episode and go into a bit more detail. You listen to the podcast, right?

      Comment by Stuart Robbins — June 19, 2012 @ 12:21 pm | Reply

      • Well, read the transcript. Very interesting.

        Comment by Expat — June 20, 2012 @ 7:45 am

  2. I enjoy the puzzlers but have never sent in an answer (until this morning) mostly because by the time I get to a computer I have to work! After doing a little research to try to answer it I realize how much work you have to put it so I wouldn’t blame you if you dropped it.

    Comment by Richard C — June 22, 2012 @ 9:56 am | Reply

    • Thanks Richard, and FYI, you’re the first to get BOTH parts of this puzzler, so at the moment (unless someone writes in somehow with an even more complete answer), you’ve won.

      Comment by Stuart Robbins — June 22, 2012 @ 9:59 am | Reply

  3. I enjoy the puzzlers, but I don’t often get around to listening to the podcast before the next one is already out. They’re fun to think about though.

    Comment by jasongoemaat — August 8, 2012 @ 1:20 am | Reply

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