Sniffing Mars's Air
The ExoMars Trace Gas Orbiter was built by ESA and Roscosmos to measure gases in Mars's atmosphere with extreme sensitivity, down to a few parts per trillion. It has not found the methane that earlier observations reported, setting very low limits on how much there can be, but it made the first detection of hydrogen chloride in the Martian atmosphere and has tracked how Mars loses its water.
Ten Years at Mars
TGO entered orbit on 19 October 2016, the day its Schiaparelli test lander was lost. After almost a year of aerobraking it began science in April 2018. Its CaSSIS camera has mapped more than a tenth of the surface in colour, and its radio relays data for NASA's Curiosity and Perseverance rovers. It is also planned to relay data for ESA's Rosalind Franklin rover.