The Moon Has a Fluid Outer Core

mapkinase writes with this excerpt from Discovery News: "The Apollo Passive Seismic Experiment recorded motions of the ground from moonquakes and other activities generating sound waves until late 1977. The network was too limited to directly monitor waves bouncing off or scattered by the moon's core, leaving scientists dependent on more indirect techniques, such as measuring minute gravitational changes, to craft a picture of the moon's interior. Those models turned out to be pretty accurate, says lead scientist Renee Weber, with NASA's Marshall Space Flight Center in Huntsville, Ala. The new research confirms the existence of a solid inner core and liquid outer layer, similar to Earth's. Unlike Earth, the moon also has a partly melted, mushy layer over that."

Comments

Re:Heat energy.

[RsG]

IIRC, there's still some debate as to how much of the interior heat of the Earth is due to radioactive decay and how much is residual heat leftover from the planet's formation. Remember that the Earth/Moon system originated as two bodies of similar mass that collided a few billion years back; both would have been fully molten, surface to core, when the proverbial dust had settled. Millennia would pass before either had a solid surface.

It might be that the internal heat of the Earth is partly residual, with radioactive decay delaying cooling by adding more heat. Regardless of the proportion of residual to radioactive heat, the moon should be less molten than the Earth, if only due to the square-cube law dictating the Earth will cool more slowly. So the science in TFA is actually pretty interesting.

Re:And yet,

[icebike]

Looks a lot like other moons, and even like Mercury, and not totally unlike Mars.

Its the only moon in a warn (not hot, not frozen) zone, and its far from uniform.

If it was totally solid you might expect more landscape features created by impact. But because it is simi-fluid and reasonably large, gravitational forces keep super-large scale features from being formed.