Bella's parents have trouble being married.
It's not any one thing, exactly, they aren't cheating on each other, they don't fight, they don't have screaming differences of opinion about how to bring up their child. There's just this itchy, fluttering regret about Renée, a certain tired wit's-end character to Charlie's demeanor around her. They are trying. They are trying so hard. Bella isn't sure if it's for her or out of a sense of duty to their vows or what. But they are still married.
When Bella is eleven, Charlie brings in an envelope with a Stark Industries logo on it, and says he didn't think it would come to anything, but he applied for a job, and they've unexpectedly offered him an interview, and he'll show up to it if Renée wants him to.
She asks where's the job and he says Mars and she squeals and hugs him harder than Bella's seen her do before. So of course he goes.
And a few weeks later, he's sitting, bewildered, with an offer in his hand, and they put the house on the market and start packing, and Renée's so happy, she gets to live on Mars, her baby girl (Bella is eleven entire years old, thank you very much) gets to grow up on another planet before almost anyone else, it's so exciting.
Bella isn't sure what to think about it, and all her notebooks are packed, but she supposes living on Mars is, at minimum, cool, even if she'll miss Angie and her other friends. And she can't really do anything about it, anyway.
The trip is weeks long - although not months; that's part of why they're willing to hire people like this, now - and boring, after the initial tour of the ship.
Bella is almost the only child on the entire colony. There are some teenagers - prodigy interns, and one person's seventeen-year-old son - and then there's her and that's almost it, except that Howard Stark himself, and his family, are living on the colony now for hands-on work with the ruins, and Howard Stark has a boy her age.
Bella sets out to meet this boy, if he's going to be her only potential playmate in her own age range for the foreseeable future.