Alexander Gerst (born 3 May 1976 in Künzelsau, Baden-Württemberg) is a German European Space Agency astronaut and geophysicist, who was selected in 2009 to take part in space training. He was part of the International Space Station Expedition 40 and 41 from May to November 2014. Gerst returned to space on 6 June 2018, as part of Expedition 56/57. He was the Commander of the International Space Station. He returned to Earth on 20 December 2018. After the end of his second mission and before being surpassed by Luca Parmitano in 2020, he held the record for most time in space of any active ESA astronaut (362 days), succeeding Italian astronaut Paolo Nespoli, and German ESA astronaut Thomas Reiter, who formally held the record for the longest time in space for any active or retired ESA astronaut. Education and research Gerst graduated from the Technical High School in Öhringen, Germany, in 1995. While in high school, he volunteered as a scout leader, firefighter, and water rescue lifeguard. Gerst studied at the University of Karlsruhe (now Karlsruhe Institute of Technology), Germany, where he received a degree in geophysics with distinction. From 1998 to 2003 Gerst participated in several international scientific collaborations and field experiments, including some in remote locations such as Antarctica. From 2001 to 2003, Gerst studied for a master's degree in earth sciences at Victoria University of Wellington in New Zealand. While researching his master's thesis, he developed volcano monitoring techniques that might improve forecasts of volcanic eruptions. His results were published in Science Magazine. Gerst worked as a researcher at the Institute of Geophysics at the University of Hamburg between 2004 and 2009, and received his doctorate in natural sciences from the University of Hamburg in 2010, with a dissertation on geophysics and volcanic eruption dynamics at Mount Erebus volcano in Antarctica. In 2007 Gerst received the Bernd Rendel award for outstanding research from the German Research Foundation (DFG). He has published several papers, including one in Nature. In ESA Gerst was selected as an astronaut in 2009 by the European Space Agency. In September 2019, he participated in the ESA CAVES mission of the European Space Agency alongside Janette Epps, Takuya Onishi, Joshua Kutryk, Joe Acaba and Nikolay Chub. In 2022, he participated in the ESA PANGAEA training course, in its sessions in Bletterbach (ITA), Nordlingen-Ries (GER) and Lanzarote (SPA) together with NASA astronaut Stephanie Wilson. Expedition