Well, we could use the prefix "astro-" for generic celestial objects, including planets. So you could go with "astrothermal". And then the study of those objec

Well, we could use the prefix "astro-" for generic celestial objects, including planets. So you could go with "astrothermal". And then the study of those objects, cf. geology, would be.... no, wait. (Is there a generic prefix for just planetary bodies that we should be using? If so, what is it? If not, why not?)