Maven, an acronym for Mars Atmosphere and Volatile Evolution, abruptly stopped communicating with ground stations on Dec. 6. NASA said this week that it was working fine before it went behind the red planet. When it reappeared, there was only silence.

Kim officially became an astronaut in 2017. Expedition 72 and Expedition 73 marked Kim’s first visit to the ISS, where he served as a flight engineer and flight surgeon for eight months while helping to conduct a number of scientific and technological research projects.