Piippor- Looks good, just not sure it really fits the nature of the Solstice. I tried to imagine a Solstice logo as well, I too started thinking about the Sun Earth relationship. The tie in to the Silver Streaks is nice too. The problem with it for me is 1) It has a very Deco look and feel to it. It would look right at home on a 30's Pontiac, or a retro sedan like the PT cruiser style. 2) It utilizes mostly vertical elements, and a roadster is a very horizontal vehicle. Vertical can imply stability, power, piety, or advancement, but it doesn't convey motion very well or youth.
Maybe try a variation on the design in the horizontal. Turn it on it's side and break the ridgid lines out of the boundry, maybe kind of like speed lines. The Sun is only overhead to us flatworlders, and in space it can be oriented any way, so maybe there's still away to convey the Summer Solstice. I do like the design, I just think it would be perfect on a retro sedan, not the Solstice. If you try another one, I'd love to see it. :thumbs