Now lets put all this into context, I know how Christians love context... Jesus' real name is Yeshua. This translates into some version of "The Lords Salvation." I ask you, "salvation" for who and for what if there are no humans who have sinned and need salvation? Why would a god in heaven have a name that means "The Lords Salvation?" That name strictly relates to humans AFTER supposed sin. Had he existed even in concept before sin his name would be more like Yahweh's... "I Am" or "I exist" or something similar. It wouldnt relate strictly to human existence.
You are extrapolating Jesus' human name back onto he's God form, thus accusing him of only being around for a sacrifice. If you instead take the view that before having the name Jesus given to him whilst on Earth, he was called "The Son", then this doesn't make any sort of implication that that was he's sole purpose.
As for Mercury the planet, apparently its purpose is to declare the glory of god!
Psa 19:1 The heavens declare the glory of God; and the firmament sheweth his handywork.
I was merely working on what you seemed to be claiming, that Jesus only exists because he has a purpose, and was then asking what Mars' purpose was. But I'm assuming this is purely having a go at what I said.
Even though technically Jesus doesn't have to have a purpose to exist, it sure was convenient that Yahweh was/had a sacrificial "Son" handy. Imagine if he'd been a Duality with just Father and Holy Spirit. "Well, I can't go, because I'm the one whose wrath the sacrifice is supposed to appease, and I can't send Him, 'cause crucifying the Holy Ghost would be like trying to nail Jell-O to a wall. Whelp. Guess the Devil wins."
I'd hardly call him a "sacrificial son". I mean, they 3 of them co-existed from before the universe, and he didn't sacrifice him as you put it, he chose to let he's son come to earth, and be sacrificed for the sins of human kind.