David, Yes. There is a slide control on the upper left, just move that to zoom in or out.
The map should come up as a world map when you first open it.
As to other planets, I am afraid only the 3rd rock from the sun is represented right now. When Google maps add more areas, I am sure your celestial body will be available.
Since it has a degree of privacy built in, your exact location is not provided, (it is only by zip code or city name) it is indicated by general area. That is why if you zoom really in, some people are shown as living on rail road tracks, the middle of a lake or freeway.
“It’s a damn poor mind that can think of only one way to spell a word!”