NASA Astronaut and Roscosmos Cosmonauts Conclude Eight-Month ISS Expedition 73

NASA astronaut Jonny Kim and Roscosmos cosmonauts Sergey Ryzhikov and Alexey Zubritsky concluded their eight-month science expedition aboard the International Space Station (ISS) with a safe return to Earth on Tuesday, December 9, 2025. The crew undocked from the ISS on Monday evening, December 8, at 8:41 p.m. EST, utilizing the Soyuz MS-27 spacecraft for their descent. This departure formally concluded Expedition 73 operations.

The Soyuz MS-27 executed its parachute-assisted landing on the Kazakh steppe, southeast of Dzhezkazgan, precisely at 12:03 a.m. EST on December 9, following the standard deorbiting sequence. During their 245 days in orbit, the Expedition 73 crew orbited the planet 3,920 times, covering a total distance approaching 104 million miles. This mission marked the first spaceflight for both astronaut Kim and cosmonaut Zubritsky.

Expedition 73 Commander Sergey Ryzhikov completed his third mission to the orbital complex, bringing his career total to 603 days in space, positioning him 13th on the all-time duration list. Prior to undocking, Ryzhikov transferred command of the ISS to NASA astronaut Mike Fincke on December 7 during a ceremony, with Fincke now leading the Expedition 74 crew to ensure operational continuity.

The crew performed a diverse portfolio of scientific investigations critical for advancing terrestrial and deep-space research. Key activities for Kim included studying bioprinted tissues incorporating functional blood vessels for regenerative medicine research and evaluating remote command protocols for robotic systems under the Surface Avatar investigation. The expedition also encompassed extensive research across biology, human physiology, physics, and materials science, alongside three spacewalks, including one on May 1, 2025, to install modification kits for the station’s seventh iROSA solar array.

Following the landing, immediate medical assessments were conducted for the crew within a heated tent near the site. Kim was scheduled to travel to Houston, while Ryzhikov and Zubritsky were set for transport to the Gagarin Cosmonaut Training Center in Star City, Russia, for post-flight rehabilitation. The successful return highlights the ongoing international collaboration between NASA and Roscosmos, which maintains the ISS as a microgravity laboratory as it proceeds toward its planned operational end near 2030.