> carolb wrote:
> > Which is exactly what one would expect from a body that
> > accreted from the debris of an impact.
> > Carol
> Its actually the exact opposite one would expect to find and is
> unrelated to hollow spaces.
How so? If planets, moons and asteroids are formed by clumps of irregular debris accreting and clumping together by the force of gravity, then of course there’ll be hollows in between the clumps. I had Phobos, Mars’ larger moon, in mind when I wrote that, as Phobos has such voids.
Analysis of Mars Express radio science data gave new information about the mass of Phobos based on the gravitational attraction it exerts on the spacecraft. The team concluded that Phobos is likely to contain large voids, which makes it less likely to be a captured asteroid.
It is possible that Phobos formed in situ at Mars, from ejecta from impacts on the Martian surface, or from the remnants of a previous moon which had formed from the Martian accretion disc and subsequently collided with a body from the asteroid belt. Data from the Mars Express OMEGA spectrometer suggests Phobos has a primitive composition, so primitive materials must have been available for accretion during its formation. The circular orbit suggests that Phobos formed in situ whilst analysis of the Planetary Fourier Spectrometer data from Mars Express also points towards in situ formation but does not rule out the possibility that Phobos is a captured achondrite-like meteor.
It wouldn’t surprise me if Earth had giant caverns deep down too, farther down than we’ve been able to explore.
Do you have a link for that
> statement? For such sizable hollows to form there must be
> something there that is now gone, namely a gas or liquid (water
> or lava) that was trapped or created in the bodies cooled state
> and later ejected by some process.
Not necessarily – just gaps between the irregular debris that formed the body in the first place.
There are many interesting
> holes on the Lunar surface like this:
> which are speculated to be lava domes (lava tube skylights).
> Regardless, finding these holes suggests "...it may have
> confirmed a theory that scientists had held about the Moon
> since the 1960s - its surface may hide a vast network of
Yes, collapsed lava tubes can easily account for holes near the surface, which you’ve shown photos of. If this is what you had in mind when you responded, then I misread what you said, and thought you were referring to deep voids, the kind I mentioned above.