NASA's new class of astronaut candidates will likely have a shot at being among the first humans to visit Mars. That, plus media coverage of commercial space flight and a major social media push, may have contributed to a record 18,300 applicants. In the end, twelve were selected, including Loral O'Hara , a research engineer at Woods Hole Oceanographic Institution (for two more months). Plenty of kids say they want to be an astronaut when they grow up, but O'Hara has actually been working toward