[Steely Tom]

I can understand how an object can approach Earth, get slowed just enough by skimming the atmosphere to then go into a stable (or semi-stable) orbit, and then eventually fall into that atmosphere.

I can't understand how an object — once having done this — can then (some time later) leave Earth orbit and go on about its merry way. Unless it has some sort of propulsion capability.

[Kickass Conservative]

It took off when it noticed some F-18’s approaching.

[tet68]

Not sure about that either.

Maybe it realized it was an election year.

[DannyTN]

It’s mother called.

[17th Miss Regt]

It left due to climate change.

[spudville]

I was wondering how it could be “blazing” in the vacuum of space.

[PapaBear3625]

I can't understand how an object — once having done this — can then (some time later) leave Earth orbit and go on about its merry way. Unless it has some sort of propulsion capability.

I'm going to guess an interaction with the moon might do it.

[fruser1]

It can happen because the atmosphere does not have homogenous density on the fringes. Plus it expands and contracts due to solar variance.

[Phlyer]

I can understand . . . skimming the atmosphere . . . stable (or semi-stable) orbit, and then eventually fall into that atmosphere.

Your questions apply to a two-body problem, which the solar system is not. However, if an object 'skims' the atmosphere (in a two-body problem) it will not enter anything like a stable orbit. If it manages to get back above the atmosphere (doesn't re-enter immediately) then it still has less energy than before it made its skim. The next pass perigee will be no higher, and lose even more energy. It will re-enter in a few orbits at most.

The minimoon situation results from having multiple bodies. Consider an object that is passing by the Earth with barely enough energy to continue without being captured. Then put Jupiter 'behind' the object as it passes the Earth. The object can be slowed down just enough to be captured by the Earth - even without touching the atmosphere.

I can't understand how an object . . .Unless it has some sort of propulsion capability.

This is the same situation in reverse. At some later time, if the minimoon is just passing the Earth when Jupiter is ahead of it, then it can be tugged back into a non-Earth orbit (still in orbit about the sun).

If the minimoon passes again when Jupiter is behind it, even if it didn't skim the atmosphere when it became a minimoon, it can be decelerated enough to enter the atmosphere.

Of course, there are more solar system objects than just Jupiter, and because the Earth's orbit is not a perfect circle, the sun can accelerate objects at just the right moment. If enough effects add up together they don't have to be aligned just as the object is passing the Earth.

The common denominator is that the objects, at least as they are captured or escape, need to be right on the boundary of enough energy to orbit - which is the case if they just wander by in a solar orbit with parameters close to the Earth orbit.

[Boogieman]

“I can’t understand how an object — once having done this — can then (some time later) leave Earth orbit and go on about its merry way.”

Perturbation from the moon probably. You have to remember that there are more than just 2 objects in the orbital system of the earth and the object that gets captured.