Ed Gold, an Australian born in 2008, was second in command at Bowie Base One. On several occasions he would try to take heroic or commanding actions, only for Captain Adelaide Brooke to order him back to his post; the two had an edgy relationship.
In his early life, he was fascinated by space travel. He became a US citizen in 2040 in the hopes of becoming a NASA astronaut, but would return to Australia in 2044 to campaign for an Australian space programme; he argued that the country had the infrastructure, industry, and university base to achieve this. His campaign led to the construction of a space elevator off the coast of Western Australia.
In 2059, when the Flood attacked the base, he witnessed several members in his crew get taken over. When the Doctor was taken into the Base he thought he was the culprit. He was later proved wrong. When the severity of the infection became clear, he reminded Brooke of the evacuation protocols and was ordered to prep the base's shuttle.
While the shuttle was successfully prepped, the infected Maggie Cain got in and infecting him by shooting water up the shaft to the cockpit. To keep the infection reaching Earth, he caused the rocket to self destruct before he fully transformed. (DW: The Waters of Mars)