 Freema Agyeman told the school publication "The Newspaper" that Martha is older and more secure than Rose.Agyeman speculated that Martha, by contrast, travels with the Doctor for the adventure, rather than because of a need for guidance or education (Agyeman also told "The Newspaper" that Martha hopes to eventually go back to Earth and finish her medical education).In addition, Martha's family appears to be of a higher social class than Rose; whereas Rose's family was fairly typically working class, Martha's family appears to be wealthier (her father owns what appears to be a late model Mercedes-Benz convertible, and the clothes worn by her family are substantially more in line with fashion), probably middle to upper middle class.