Yuri Kerenski

Yuri Kerenski was a Russian nurse and part of the Bowie Base One Mars colony.

Early life
Born in 2032, Yuri grew up with a brother, Mikhail, who later went to live with his husband, George, in Dagestan. (TV: The Waters of Mars)

Career
Yuri initially had a low-level research position in the Russian Federal Space Agency and trained as a nurse in order to progress. He ended up earning the favour of the Director General after treating him, and was given a higher nursing position. This led to him training at the Johnson Space Centre and befriending Tarak Ital; Yuri stayed in the US, and Tarak recommended him as the nurse for the Bowie Base mission. (TV: The Waters of Mars)

Colony on Mars
Whilst on Mars, he began a secret relationship with Mia Bennett. (PROSE: The Waters of Mars) A known joker, Yuri used a spare solar panel to make a "No Trespassers" sign outside the base. Later, he looked after a quarantined Maggie Cain after she was infected by Andy Stone.

He was destined to die in an explosion of Bowie Base One, though he managed to escape along with Mia and Adelaide Brooke, when the Tenth Doctor interfered with the course of events and rescued them. In the timeline where he did die, he was posthumously awarded the Hero of Russia title.

In the altered timeline, Yuri and Mia revealed the events of Bowie Base One and Adelaide's heroic actions to the world. Both Yuri and Mia later travelled with Adelaide's granddaughter, Susie Fontana Brooke, into space. (TV: The Waters of Mars) He and Mia would later go on to have a daughter together, whom they named Adelaide after their former captain. (PROSE: The Waters of Mars)

Behind the scenes

 * The details of his pre-Bowie Base career can be briefly seen in his obituary.
 * In a deleted scene, it was revealed he and Mia were in a relationship and kept it secret as Adelaide wouldn't allow romantic relationships. When the Doctor exposed it, the crew revealed they knew all along including Adelaide who chose to ignore it but was forced to take action to keep the two apart after it was exposed. But even though his storyline wasn't introduced, the writers still seemed to keep some sort of relationship, that none of the other crew had, between them both. This relationship is briefly implied in the episode when at one point, Yuri and Mia briefly hold hands during the crisis and was included within the novelisation.
 * In another deleted scene, he did not understand why the Doctor was unaware of the Carbon Wash, which the Doctor mistook for snow. He later stopped seemingly to speak to the Doctor whilst following Mia, but was put off by the Doctor glaring menacingly at him. This clearly scared him and caused him to continue his departure.