I have a question regarding the authenticity of Google Earth images. Are they always real satellite photos, or can they be modified with photo editing softwares? (By "modify" I don't mean touch-ups to boost clarity, but adding/removing/altering features on the satellite images.)

The following locations show what appear to be slogans engraved on the ground in mountainous areas in Northwestern China.

Location 1:
42� 39' 25.03" N
94� 10' 03.53" E

Location 2:
42� 32' 32.87" N
94� 19' 33.80" E

Location 3:
42� 27' 09.33" N
94� 08' 49.88" E

And the strangest of all - Location 4:
40� 27' 08.62" N
93� 44' 34.43" E

Are they real?

Thanks in advance.