Fra Mauro

by Dave North

Went up to Fremont Peak Saturday night to do the moon program, which was pretty much a failure.

When we got there it was mostly cloudy (the cotton candy kind) and though over 40 people showed up to listen to me blather on about the moon, the sky did not cooperate at all, and there was little to be seen when I was through. They were a good-natured crowd, but disappointed a bit as they straggled away.

Of course, fifteen minutes later it cleared up and stayed that way (with awfully good seeing) for the rest of the night.

To console ourselves, we hooked up a binoview to the 30-inch and plugged it wide open into the moon.

The images were stunning almost without exception (particularly fun was seeing *all* the mapped secondaries of Copernicus, noting the way they bunched up around the rim of Stadius -- Rukl 32).

But my eyegrabber of the night was Fra Mauro, a mostly-ruined crater near Maria Insularum and Cognitum (Rukl 42). Fra Mauro is well-known as Mickey Mouse's face, when combined with the "ears" Parry and Bonpland (this "selenism" is best seen in a reflector).

Rukl only hints at the striations, cracks and blobs in the floor of this old plain -- probably overlaid by ejecta from the Imbrium Event.

Apollo astronauts picked up some of this crud, which is generally referred to as the Fra Mauro formation for fairly obvious reasons, making those samples the genetic source name of stuff seen over roughly half the surface of the moon.

In this case, I'd have to go with the "aperture rules" arguments, since I had never seen this level of detail in Fra Mauro before, though I have visited quite a few times with smaller scopes (usually between 4.5 and 12.5 inches).

Almost every linear feature on the floor (and most features are linear) was radial to Imbrium, many of them with a clearly "hummocky" look, some with an almost rolling character to them.

Also, some of the secondary craterlets seem to be part of a loose string leading back to Copernicus. There is quite a bit of history to be read in this old wreck of a crater... and the more of it you see, the better it gets.

We saw quite a few other fascinating things that evening, but I'll leave that to other folks, or perhaps just other days.