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http://www.space.com/21364-moon-gravity-mascons-mystery.html writes to say

...These geologic structures, called mascons (short for mass concentrations), are so dense they alter the moon's gravity field, causing perturbations that can tug a spacecraft lower in its orbit around the moon, or push it wildly off course...

Lacking an atmosphere, perhaps Luna exhibits the acute form of this malaise. If a celestial body -

  • lacks an atmosphere,
  • has a superficial/non-existent magnetosphere, and
  • has a near solid core

would it follow that it would have lumpy gravity?

What celestial bodies are known to be lumpy in gravity?

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    $\begingroup$ IIRC, every rocky world has lumpy gravity to some degree. Obviously Luna's gravity field would be lumpier than Earth's. I'm not certain how much those other factors you mentioned affect lumpiness though. As far as I can tell, it is mostly due to the distribution and density of the mascons. $\endgroup$ – called2voyage Aug 28 '13 at 12:50
  • $\begingroup$ In one scenario the earth and moon are a result of a collision of two bodies. If this were true early earth would have had the same mascons as the moon unless they have melted. $\endgroup$ – James Jenkins Aug 28 '13 at 15:23
  • $\begingroup$ @JamesJenkins That would only be true at the point of separation, if even then. Mascons can be induced by meteor strike, among other things. $\endgroup$ – called2voyage Aug 28 '13 at 19:38
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What you are looking for is a formal way to measure the "lumpiness" -- this is the spherical harmonic model of a body's gravity field. These models are pretty well known for the earth and moon as they are critical for trajectory analysis.

This paper gives some nice plots that visualize and compare the harmonic models of various planets: http://www.ipgp.fr/~wieczor/MyPapers/WieczorekTOGSubmit.pdf.

The math can be daunting, so sometimes this is simplified by describing a body's geoid -- the shape that the surface of the oceans would take under the influence of Earth's gravity and rotation alone.

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