[X] My Assistant

[Phil Stooke]

People might like to see this:

A collection of all useful Lunar Orbiter images has recently been added to the fabuolous offerings at the Lunar and Planetary Institute website. Here's the link:

http://www.lpi.usra.edu/resources/lunarorbiter/

Thumbnails lead to good scans. This is the best online collection of Lunar Orbiter data yet available, and it should lead to many hours of wasted time.

Phil

[dvandorn]

Oh, I wouldn't say that, Dan. I'm still planning on dropping the $$$ for Phil's book, when I can.

But yes, the site is engrossing. I just spent a half hour locating the LOIII images of the eventual Fra Mauro landing site. The landmarks are obvious once you find it. It was nice to see a lot more of the context of the general area (Imbrium ejecta field) and identify some of the things I had heard about but never clearly seen, such as what I'm sure was Star Crater (the original primary EVA goal for the site) and the lobate, layered, almost feathered-looking northern extension of Cone Ridge.

While that site was worthwhile visiting on any of the landings, I could almost have wished for a J mission there. I see a ton of interesting depositional landforms that would expose some pretty diverse rock types, I think.

Then again, the rocks from Fra Mauro were found to be breccias of primarily basaltic gross composition. Not only were the clasts in the breccias primarily basalt, the matrices of the breccias tended to be basaltic. So while the Fra Mauro formation, a huge, almost ropy splash of ejecta from the Imbrium impact, may look really interesting, it seems to have been created mostly from basaltic mare materials that were excavated and altered. Either that, or this portion of the Imbrium ejecta represents a large pocket of basaltic magmas that were excavated.

I'm not certain that even Imbrium excavated completely through the lunar crust and down into an upper mantle of basaltic magma -- but it's not unlikely that huge magma chambers could have formed in the Moon's ancient upper crust. Excavate one of these and you'll generate a fair amount of the kind of brecciated ejecta as we see at Fra Mauro. But this basaltic composition makes Fra Mauro entirely dissimilar to the true highlands formations visited by the three J missions (well, OK, two highlands-derived basin wall mountain locations and one true highlands location). Highlands materials have a relatively poor admixture of basaltic materials, with a dominance of noritic/troctolitic aluminum-rich rocks. That's why I tend to chafe a bit when Fra Mauro is defined as a "highlands" site. It's not -- it's an Imbrium ejecta site. It's morphologically and compositionally distinct from the lunar highlands.

-the other Doug