I saw a post somewhere (typed in some keywords to search for it but no luck) that said you could tell an earthlike/amonia planet by the sounds it makes? .... Can someone explain this to me? ... im going to be doing some exploring soon.
The different planet types have distinct sounds when you hover over them in the system map which you can use to decide if a given planet is worth the SC trip to go scan it. Use http://www.objectscanner.net/ for reference of the sounds, the Cr values listed are old and an order of magnitude low.
I found that I had to have the in-game music turned on to hear; though I've had people tell me that that is a bug.