Initial results from the MAVEN mission to Mars

The Mars Atmosphere and Volatile EvolutioN (MAVEN) Mars orbiter has been gathering information on the Mars upper atmosphere, ionosphere, and solar and solar wind interactions since its orbit insertion in September 2014. MAVEN's science goals are to understand processes driving the escape of atmospheric gases to space at the present epoch, and their variations with solar and local heliospheric conditions together with geographical and seasonal influences. This introduction and the accompanying articles provide a selection of key results obtained up to the time of writing, including measurements of the overall geometry and variability of the Martian magnetosphere, upper atmosphere, and ionosphere and their responses to interplanetary coronal mass ejections and solar energetic particle influxes. The ultimate goal is to use these results to determine the integrated loss to space through time and its role in overall Mars atmosphere evolution.