I have been trying to look for this book for a while. I think it was made for children. My memories of it are vague. On the cover I think there is a picture of a young girl with purple hair and she's smiling. In this book I think she and some others travel into space. I distinctly remember there being "alien" characters being shown in the book. By characters I mean letters. It's a sci-fi book, that much I'm sure of. Perhaps she is traveling with an older man? Any suggestions that'd point me in the direction of that book would be greatly appreciated.
I finally found the answer after so many years. It's the Akiko series. When I asked this question I was referring to Akiko on the Planet Smoo. Thank you to everyone else who tried to help.
My first instinct is Sassinak, by Anne McCaffrey and Elizabeth Moon. Space travel, smiling girl. Older man adopts the main character.
But purple hair only if the cover is sun bleached.