I saw a list of top free apps in a magazine. Yeah, one of those old fashioned things with glossy paper made from dead trees. Anyway, the SPARQCode yielded an app not found message from Android Market. I'm guessing that means it used to be available? Do you know if it is available, was available, or will be available in the future?
Google Earth is definitely available, I can see it in my Market right now, however it needs Android 2.1 as a minimum to work, so if your phone is running an older version of the OS, then you won't be able to see it as the market hides apps that it knows definitely won't work on your phone.
See the note at the bottom of this page, where it says that it requires 2.1 http://www.google.com/mobile/earth/