Can a Planet's Surface Be in Orbit?
I've been revisiting a lot of old SF recently, primarily Larry Niven. He's well-known to be one of my personal heroes, but I'll admit that he's a mixed bag. Consider the Smoke Ring/Integral Trees novels. The problem here is that Niven had one of the most brilliant concepts in SF-an immense, air-filled toroidal region around a star that supports life in the absense of a planet, at zero-G-and the stories are about little more than petty politics. Against the titanic scale of the Smoke Ring, almost nothing happens.
Oh, well.
But reading The Integral Trees made me wonder if that's the only way you can have a naturally occurring Earthlike atmosphere at zero-G. I flashed on Mission of Gravity, which is a planet forced into an ellipsoidal shape by its rapid rotation around its axis. The gravity at the poles is 700G, dropping to only 3G at the equator due to centrifugal force. Now, suppose you had a smaller planet than Mesklin, but one rotating a lot more rapidly, so that gravity measured at the poles is 1G or somewhat less...but the equatorial bulge is moving so quickly that it-and its atmosphere-are in orbit.
On the surface, this seems plausible, if unlikely. Such a planet might not be quite "solid" in the same way that most rocky planets are. The equatorial bulge might be fragmented, and consist of Rhode Island-sized chunks of rock (and down from there) just drifting along, bouncing off one another due to local thermal turbulence in the atmosphere.
Toward the center of gravity a little you get a certain amount of downward force, enough to gather immense chunks of rock into a sort of air-permeated matrix, but not enough to force them into a solid crust. I suspect that this situation might not be stable over geological time-remember, you have a sort of "perpetual downhill" as you move away from the equator, and a certain number of those rock chunks would periodically fall toward the poles.
But still...it's an interesting notion. What sort of life would such a place support? Where would the water be? What kind of fun could you have in a place where you could just jump off the side of a mountain-and let the wind carry you along toward another mountain?
Will I write about it? I'm just not sure. I have relatively high confidence in the concepts that I actually write stories around. I don't have quite such confidence in this one. Let me think about it for awhile. I'll get back to you.