Dreams and goals, by their nature, contain an element of the impossible. If they didn't, they'd be just be ordinary activities we take for granted (although, interestingly, one person's ordinary activities are often another person's dream).

For Dorothy Metcalf-Lindenburger, a former teacher who became an astronaut and is now a geologist for a private firm, she knew from a young age that she wanted to be all three. And though the three dreams seem separate, they share an appreciation for science she developed in elementary and middle school, sparked by projects like distilling fruit food waste...