This distinctive dark "sea", close to the north eastern limb of the Moon, is highly unusual in being separate from the other seas. It appears as a
neat oval measuring about 270 miles north-south and 180 miles east-west (actually 350 miles correcting for foreshortening) ie roughly the size of
Ireland.
This distinctive elliptical Mare was originally an impact basin, subsequently filled with lava. Beneath it is a mass concentration (or mascon) - a
body of denser material which causes a detectable gravitational anomaly.
[Al also discusses the appearance of the rays from Proclus over Mare Crisium.]
[Worden, from the 1971 Visual Observation Debrief - "It's very strange the way the ejecta from, particularly, Proclus crosses Crisium. It's almost
like flying above a haze layer and looking down through the haze layer at the surface. I don't know whether you've ever had the opportunity to do
that or not, but that ejecta from that crater doesn't look like it's resting on the top of Crisium. It looks like it's suspended over it. It gives
a very filmy, very gauzy appearance to the whole thing."]
[El-Baz, from the 1971 Visual Observation Debrief - "It must be very thin."]
[Worden, from the 1971 Visual Observation Debrief - "Yes. And I guess the reason it looks like it's just draped or suspended over it is that almost
any way you look at it, if it goes through a crater or it goes through a ripple ridge or it goes through any topographic feature, it doesn't make any
difference from what angle you view it; those lines - the ejecta pattern - are straight."]
[El-Baz, from the 1971 Visual Observation Debrief - "Okay; now when the ray goes through a topographic prominence or a negative depression of some
sort, do you still see the ray through that?"]
[Worden, from the 1971 Visual Observation Debrief - "Yes."]
My friend, sadly some Earth-based telescope shot isn't very affordable:
besides, lights+shadows may really change the appearance of what we see: for example, what looks to be a crater below the feature you've pointed out,
is most likely a shadow casted by some relief: i can't tell it for sure, but the area that you've pointed up looks to be the one at the north of
Promontorium Olivium, but i'm not 100% sure: the lack of details makes it hard to
identify the lunar features, while i think that the crater Peirce is identifiable: i share this image of the area, including a map an a
Clementine UVVIS Multispectral Mosaic image, the best resolution one i'm aware of.
as always you amaze me with your knowledge of the Moon !
i understand Telescopes will distort the view because of the angle and lighting differences so i believe you are probably correct in thinking that
it's just shadow's playing tricks,
but....:
IF i am in the right spot here ? i do see something that looks to me, to be on the ridge of that crater and also looks as if it is hanging over the
edge ?
maybe i stared at it too long but i swear there is something strange going on there even if i am looking at the wrong spot
i would like to see some Apollo photo's of that area
i am not seeing the same thing so far, so it could be a trick of light as Internos has mentioned, but i am gonna keep looking and i really love that
Apollo link
nice vid, i like seeing these videos of the Moon using Telescopes. the person on the Youtube page say's it was a Ten inch reflector that captured
this shot.
obviously we are looking at a distorted view because of the angle and the shadows can play tricks on your eye's but i got to admit here that there
looks like something square inside the crater
90 degree corners on the Moon get my attention...
doubt we could find out exactly wich crater this is ?