Comet without tail.

[MuriloMoreira]

In my game any comet I find doesn't have a tail, I find it very strange I've never seen it before, I tried to see in the missions created for the comets but even the game's stock missions have this problem, does anyone know of any solution?

[Just Jim]

It is probably too far from the sun.  Once they get close enough, the tail will appear, and grow as it gets closer and closer to the Sun.  Then as it gets further away, it will fade and disappear.
This is not a bug, it's meant to simulate real life comets