Steffi Ehrlich was a character from the 2009 Doctor Who special "The Waters of Mars". She was portrayed by Cosima Shaw.
Steffi Ehrlich was a German astronaut born in 2021. She was a member of Bowie Base One.
She studied physics at RWTH Aachen University, taking a doctorate in solid state physics (2046). After that she worked at Argonne National Laboratory (in Chicago) and the University of California. In 2048, she was selected to join the German astronaut team in the European Space Agency. She was part of the crew for the tenth German moon mission in the spacecraft AWARQ. In 2051, she was married and had two children Ulrika and Lisette. Shortly after her second child was born, she was selected for the Mars mission. She initially refused to leave her family, but changed her mind after an unspecified event that devastated many parts of Germany.
During the mission, the Bowie Base One colony was compromised after the discovery of a viral Martian life-form known as the Flood. Steffi watched in horror as one by one her crewmates were infected, transformed into zombie-like creatures. As the infected water began to fill the base, Steffi became trapped in an isolated section with no way out. She watched a video of her two children in her last moments before she too was contaminated.
Steffi died along with the other Flood infectees when Adelaide Brooke activated the base's self-destruct system. The nuclear device obliterated the base and took the Flood with it. Steffi and the others who died would be remembered as heroes back on Earth.