There's a bug with Mercury's magnetic field, that's being fixed in the next patch. Other then that, I'd need to know the specific body you're having issues with.
In regards to asteroids, just generally speaking, they can't have an atmosphere like Earth or Venus does. There's a few reasons for this. You need a lot of things to come together to get an atmosphere that's stable long term.
The body needs to be big enough to hold on to the gas. Without enough downwards pressure, the gasses are going to expand outwards towards an equilibrium density. After that the Gasses are moving and vibrating around, whacking into each other and can exceed the escape velocity of the body itself. Especially at higher altitudes.
If a sun is present, the pressure of the solar wind will strip away the atmosphere. This happens to even relatively large planets like Mars. Mars would be a very different place today if it was as geologically active as Earth and had a powerful magnetic field.
More information on the science behind Atmospheric loss.
https://en.wikipedia.org/wiki/Atmospheric_escape
Topic: Cannot transform some planets (Read 2623 times)
