Actually, that wouldn’t be realistic. There is already a mild atmosphere on it. And at the angle the sun is hitting it compared to the camera, there wouldn’t be much of a halo effect anyways. Depending on several criteria, such as sun ray to camera angle, and even what lies beanth the atmosphere (ocean? desert? etc…) determines the effect of the halo or the way the atmosphere fades or is even present in the horizon. I found it handy to make a transparent sphere atmosphere, and a halo atmosphere, that you can switch between and adjust dependant upon desired affect needed and camera angle. Also, halos if not done just perfectly, make it look to sci-fi final fantasy kind’ve.