Drops of Jupiter

Austin is a troubled kid. What 17-year-old isn't? His brother Dallas is always on his back, his father is a drunk and his mother is nowhere to be found. As soon as his 18th birthday comes he's outta here. It's all he thinks about.... and then comes Jupiter, a vivid light in his world. What is it about her that is so special and why is it she seems so happy day after day?