The Sword and Laser discussion

hi guys I was wondering can anyone help me remember the name of a book I read at school. I won't lie to you I don't remember a lot of details as I was in Primary school at the time.
so it takes place on the last days of earth as the last rocket is about to leave to find a new planet to settle, the protagonist is a young girl, also I remember that everyone can take one item with them on the spaceship, the girl takes her diary. Now to skip ahead a bit, I remember that the planet they settle on have creatures that are very similar to butterflies. The last thing I remember is that the protagonist's diary becomes the settlers first chronicle of life on this new planet.
I know it's not much but I read this book about 20 years ago and I've been trying to find out for ages. thanks xx

The Green Book by Jill Paton Walsh

thank you.

Tassie Dave wrote: "The Green Book by Jill Paton Walsh"

The first chapter or so of that was in an English or Literature textbook of mine, I want to say in 5th grade (that's approx ages 11-12 for non US). I think I will add it to my list as well and finish it at some point.