Here's what we know:

* No substantial atmosphere: There is no evidence of a significant atmosphere on Miranda. It doesn't have a measurable atmospheric pressure like Earth or Mars.

* Possible trace gases: Some studies suggest the presence of trace amounts of gases like methane and nitrogen. These gases are probably too sparse to form a true atmosphere.

* Exosphere: Miranda might have a very thin exosphere, which is a very faint, outermost layer of gas that interacts directly with the solar wind.

Why is Miranda's atmosphere so thin?

* Small size and low gravity: Miranda is a relatively small moon with weak gravity, making it difficult to hold onto an atmosphere.

* Lack of volcanic activity: Unlike some other moons with atmospheres like Io, Miranda doesn't have active volcanism that could release gases into its surroundings.

In summary, Miranda's atmosphere is so thin that it's basically nonexistent. It's possible that there are trace amounts of gases present, but these are not enough to form a substantial atmosphere.