Moon "Mascons"

[jeuchler]

OK, so I just read about the 4% anomaly in gravity caused by the five or so concentrations of lava on the near side of the moon, and how it may have caused the PFS-2 satellite released by Apollo 16 to eventually crash.

http://science.nasa.gov/headlines/y2...htm?list156395

Forgive my naivete, but are these concentrations enough to be the reason that the moon's rotation keeps the near side facing earth?

Thanks.

[ozark1]

Wrong way round. The captured rotation is the probable reason for the marial lava flows to have happened (mainly) on the near side of the moon.

[Mister Earl]

Interesting. So tidal lock makes the near side more likely to experience volcanic activity?

[antoniseb]

tidal lock makes the near side more likely to experience volcanic activity?

I'm not sure how you came to that conclusion. It is entirely likely that the volcanic activity happened before the tidal lock was complete. It is also possible that the volcanic activity happened after a tidal lock was achieved, but that the Moon rotated some fraction of a turn after the masscons were formed.

We do not know the sequence of events, but the most frequently cited scenarios say the masscons came first.

[Mister Earl]

Antoniseb, that's what I thought. As far as I understand the mechanics of tidal lock, the denser part of the smaller body "points" toward the larger when tidal lock takes place.

Ozark1 said, and I quote:

Wrong way round. The captured rotation is the probable reason for the marial lava flows to have happened (mainly) on the near side of the moon.

That's what threw me off.

[antoniseb]

BTW, It is my understanding that it may have been an even chance whether the masscons would have ended up on the near or far side of the Moon. Neither should be favored.

[jeuchler]

As Jeb Bartlett (The West WIng, for all you voters) would say,

"Post hoc, ergo propter hoc"

(After it, therefore because of it...)

Thanks for straightening me out on lunar cause and effect!!

[astromark]

While the moon still had a molten core. This was some time ago. A fracture zone caused by impacting mass resulting in a lava flow long since inactive. The moon still has seismic activity. Is less dense than Earth and does not now have a molten core. I do not think tidal locking caused this effect. A unrelated result. Remember the chicken and the egg. The answer is fish.

[hhEb09'1]

Antoniseb, that's what I thought. As far as I understand the mechanics of tidal lock, the denser part of the smaller body "points" toward the larger when tidal lock takes place.

Another problem with that explanation is that the mascons do not point towards the earth. IIRC, the axis of maximum differentiation is about thirty degrees off the earth-moon line.