When working with an ArcGIS Pro 2.3 Global Scene the horizontal coordinate system cannot be changed. I found out that the horizontal coordinate system (CRS) "must always be WGS 1984 Web Mercator [I think 3857]". It is possible to change coordinate systems for maps and local scenes. Why is it not possible to change the CRS for global scenes? I am exploring options to change a Global Scene so that I might map with a different ellipsoid for example other solar system bodies.