Away on a Comet!

It is a Jules Verne novel and quite different from his other work, not just because it is impossible scientifically by modern standards (or even those of the 19th century), but because it ends in a way that satisfies the needs of the novel but also provides a way to write off the entire impossible story as a shared delusion.  Fun, in a weird sort of way.  

An asteroid of that size could carry an Earth-like atmosphere for a couple years, especially at the outer reaches of its orbit, although not very plausible at its perihelion.  The physics and astronomy are pretty good for the period.  I am not sure when the concept of low gravity on small mass bodies was first suggested but it certainly is by this time.