it may have been luscious (underneath all the ice at least imo), but it wasn't green. the aliens/angels also created the sun (or at least brought it into our orbit), which is why their hybrid descendants became sun worshippers.
pic related - ancient mythological references to the 'sun' are often the same as references to saturn. saturn was the 'eternal sun' (which is possibly even the same concept as the 'black sun') as it could be seen throughout the day and night.
https://en.wikipedia.org/wiki/Purple_Earth_hypothesis 