I'm going with this, but with a twist. The missing piece here is, who is speaking in these poems? Everybody's thinking alien watchers, but... What if these poems are written by humans in Destiny's universe, reflecting on what wonders were once within their ancestors' grasp? Imagine having historical records - nay, legends - telling of your forefathers' travels across the stars to those wandering bodies in our solar system. The fantastic thing about planets (at least, the Ptolemaic ones) is that they're visible to the naked eye. Even after losing everything, perhaps humanity constructs these poems to remember and encode those planets, once reachable but now once again distant travelers through the night sky.

Very cool idea. I didn't look at it that way but I do like that thinking. Especially since we know the game takes place in the ruins of humanities golden age. Agree to agree

Here's another possible explanation, inspired by even more sleep deprivation than the last one! What if during Man's Golden Age, we harvested these planets and terraformed the appropriate ones, and these poems discuss that? The Moon could have been used up for resources, as well as Mercury, which somewhat fits their descriptions; the Martian rose blossoming could be its first steps in terraforming. Let's hope today is Jupiter - and that it and its Galilean satellites help my wild theories here :P