The Europa Report

Dr. Unger (Embeth Davidtz), CEO of Europa Ventures, narrates the story of the Europa One mission. Six astronauts embark on a privately funded mission to Europa, a moon of Jupiter, to find potential sources of life.[4] The crew members are Captain William Xu (Daniel Wu), pilot Rosa Dasque (Anamaria Marinca), chief science officer Daniel Luxembourg (Christian Camargo), marine biology science officer Katya Petrovna (Karolina Wydra), junior engineer James Corrigan (Sharlto Copley), and chief engineer Andrei Blok (Michael Nyqvist).
After six months of mission time, a solar storm hits the ship, knocking out communication with mission control. Blok and Corrigan perform an EVA to repair the system from outside, but an accident rips Blok's suit. While he is being guided back into the airlock, Blok notices that Corrigan's suit has been coated with hydrazine, and he cannot enter the airlock or else he would contaminate the rest of the ship. Blok attempts to save Corrigan by taking him out of his suit, but he blacks out from a lack of oxygen. Knowing there is no hope for himself, Corrigan pushes Blok into the airlock, thus propelling himself away from the ship as it continues its journey to Europa. Stranded, he dies in space. Corrigan's death demoralizes the crew, who continue with the mission.
At twenty months, the ship lands safely on Europa, but misses its original target zone. The crew drills through the ice and releases a probe into the underlying sea. Blok, who is sleep-deprived and eliciting concern in the rest of the crew, sees a light outside the ship. However, he is unable to record it or otherwise convince the crew of its occurrence. The probe is struck by an unknown lighted object, and contact with it is lost.
Petrovna insists on collecting samples on Europa's surface. After a crew vote, she embarks on a walk outside. Analyzing the samples, Luxembourg discovers traces of a single-celled organism. Petrovna sees a blue light in the distance and decides to investigate it. As she approaches the light, the ice below her breaks and she falls through. Her head-mounted camera continues to broadcast, displaying her terrified face as the blue bioluminescence is reflected in her eyes, before cutting out.
The crew agrees to leave in order to bring their discovery back to Earth, but the engines malfunction. As the ship hurtles back to Europa's surface, Xu unbuckles from his seat to remove water shielding to reduce the impact speed. Remarkably, the ship crashes at the originally-targeted landing site. On impact, Xu is killed, and the ship is damaged, leaking oxygen and losing heat. It begins to sink into the ice.
Blok and Luxembourg suit up to make repairs outside the ship. Luxembourg tries to descend, but falls through the ice. Blok knows that there is no chance that he alone will be able to repair the ship before it sinks. Instead, he manages to fix the communication system, at the expense of turning off the life support systems, just before the same blue light Petrovna saw approaches and he appears to fall through the ice as well.
Dasque re-establishes communication with Earth. All the collected images and data that have been saved over the blackout months are sent, just as the ice cracks and the ship begins to sink. Alone and anticipating her death, Dasque opens the airlock to flood the ship in hopes of revealing the source of the light. As the water rises to the cockpit, she sees a tentacled, bioluminescent creature[5] rising toward her, before the camera cuts out.
In the epilogue, Unger confirms that the crew of Europa had discovered life, and exceeded every expectation, as the footage plays from an earlier scene of the crew posing in front of the camera.

Question: Who discovers traces of a single-celled organism?
Answer: Luxembourg; Luxembourg