Mars Express and ExoMars Trace Gas Orbtiter - mission status & science highlights

Abstract

Mars ExpressMore than two decades after its launch in June 2003, Mars Express remains a dependable, highly productive and innovative mission.Recent science highlights include (1) continued mapping of subsurface reflectors beneath the south polar layered ice deposits, and associated work to explain the cause of these reflections; (2) a global map of minerals on Mars with 200 m/px resolution, obtained from analysis of infrared spectra; (3) release of 50 m resolution Digital Elevation Models based on HRSC stereo topography for quadrangles covering an ever-increasing proportion of the global surface; (4) a global climatology of ozone and water from both nadir and occultation observations and its relation to atmospheric dust; (5) transient atmospheric phenomena, such as a recurrent orographic cloud feature at Arsia Mons; (6) detailed investigation of the ionospheric structure, its variability, and coupling to the lower atmosphere; (7) continued monitoring of both the upstream solar wind conditions and of downstream escaping ions; (8) detailed study of Phobos during flybys at altitudes as low as 50 km.Spacecraft and instrument teams continue to implement new and improved observation modes. One example is new MARSIS instrument software which now allows raw data to be returned from much longer subsurface sounding passes, improving the search for basal reflectors beneath polar ice caps; another example is mutual radio occultation observations between Mars Express and ExoMars Trace Gas Orbiter, potentially providing vertical profiles of ionospheric electron content with good spatial and temporal coverage.ExoMars Trace Gas OrbiterTGO has now completed almost three full Mars years since reaching its science orbit in April 2018.Highlights include (1) continuing non-detection of methane, with upper limits as low as 20 ppt by volume. Reconciling this continued non-detection by TGO with the background levels of several hundred ppt in Gale crater by MSL remains an enigma, stimulating further research. (2) detection of HCl, the first reported halogen-containing species in the atmosphere of Mars. (3) further detail of the transport of water to high altitudes, a critical step in the escape of water from Mars. and (4) continued acquisition of 5 m colour imagery and digital elevation models over a wide range of terrain and target types, including landing site characterization.Funding for extending both missions was recently secured and is currently in place until end 2026 (Mars Express) and end 2025 (Trace Gas Orbiter).