Jack Applin submitted this B.C. strip as a CIDU, noting that “Grog hit the ball to … Saturn? Let’s ignore the [80 minute] light speed delay [one way!]. What is that film around the planet and rings? Atmosphere? But Saturn is a GAS GIANT — all that we see is atmosphere inside the rings!“
The obvious astronomical destination would have been a black hole, but that would have been impossible to convey to readers, and the closest known black hole is 1500 light years away.
My guess is that Mason chose Saturn because it is the only planet that could possibly be recognized in comic strip resolution. Most papers that still print daily comics do so in monochrome, which could seriously deteriorate the carefully shaded images in the first three panels.
P.S. Just a week later, a very similar gag appeared in The Wizard of Id:
Both strips have a long history of using golf gags, but a little more temporal separation between these two might have been advisable.
Comics I Don't Understand 
If I recall correctly, B.C. historically depicted all manner of non-standard celestial objects in the prehistoric sky. I wouldn’t assume this is Saturn, specifically, just a “generic exotic celestial body”.
Closer examination of the final panel in each of the two strips shows that Mason does not play as much golf as his grandfather did. The king’s clubhead is pointing in the wrong direction, and both players have their hands swapped: for a right-handed player (as both of them are swinging), the left hand should be at the end of the club.
nice!!
That’s a black hole, or as close as his drawing style can get. A while back a new simulation of how black holes look was devised for a movie (Interstellar). https://cerncourier.com/a/building-gargantua/ describes how it was made.
I was very dubious of Dvandom’s claim (I mean, look at the coloring! Those are Saturn’s atmospheric bands!), but then I looked at his link, and there is no doubt that that is the source of the image in the comic. (Look at it yourself!) But then, what? the colorist didn’t get the memo and assumed it was Saturn and so added the typical Saturn coloring and banding? Epic coloring fail….
I’ve always thought that ‘hole in one’ didn’t quite work. Now, ‘one in a hole’ seems perfectly reasonable. (Yes, I know it’s ‘one shot’. Work with me here.)
Thanks to Dvandom @4, we now know that the nearest black hole is not 1500 light years away, it’s at your nearest movie theater.