[Rockhounds] Supercomputer Simulations Reveal How a Giant Impact Could Have Formed the Moon

[Alan Silverstein]

Dora,

> I thought it was pretty simple.  Small planet came in, hit the earth
> at an angle, the force melted the moon and the earth and then a big
> chunk flew off, or something of the sort, there could have been some
> reaggregation.  Don't need 10 engineers trying to change a lightbulb
> to understand that.

It's NOT that simple.  Orbital mechanics (I'm no expert, but I know this
much) say that when you throw something up in the air, it returns
to/through the same path.  To get a body with the proper vector to stay
in a stable orbit requires some complex interactions; hence the modeling
being reported.

This is the same reason that after rockets launch vertically they start
(nearly immediately) to pitch sideways, and spend most of their ascent
adding to their tangential momentum, not just climbing out of the
atmosphere.

Now something I've always wondered is how any satellite gets captured by
a planet.  It should arrive and then depart hyperbolically relative to
any stable orbit, yes?  It requires at least interacting with a third
body (or disk or whatever) already near the planet to alter its path and
shed some energy?  So if Phobos and Deimos (moons of Mars) were captured
asteroids, how did they end up in orbit?

Cheers,
Alan Silverstein