Our solar system’s fourth planet is a fascinating world, and its atmosphere is a critical component of the entire Mars system. Recent discoveries by orbiters and rovers of liquid water flowing on the surface at present and in the past have highlighted the Earth-like character of our neighbor, yet these liquids wouldn’t flow without the atmosphere. Consequently, understanding the history of the atmosphere, specifically the integrated loss of matter to space through time and its role in the overall atmospheric evolution, is a critical step in determining Mars global evolution.

To address it, NASA’s MAVEN spacecraft has been in orbit around Mars since September 2014, seeking to understand processes driving the escape of atmospheric gases to space at present and their variations with solar and local heliospheric conditions together with geographical and seasonal influences. The first data are in (and archived in NASA’s Planetary Data System [http://pds.nasa.gov/]), and a special collection of papers simultaneously in Geophysical Research Letters (GRL) and Science provide a large number of key first results, including measurements of the overall geometry and variability of the magnetosphere, upper atmosphere, and ionosphere, and their responses to interplanetary coronal mass ejections and influxes of solar energetic particles. Four of the GRL papers provide an overview of the results and are offered with free access for a limited time.

This work is a remarkable achievement of the MAVEN team and the broader scientific community. Exciting new results from 10 new instruments are detailed in the 44 GRL papers and 4 Science papers. The necessary coordination takes advantage of the expertise of the MAVEN team and the best practices of the GRL and Science publishing philosophies to maximize the transfer of knowledge to the community. This community also played an essential role in the collection’s creation because the large influx of related papers necessitated a diligent pool of reviewers working within GRL’s short turn-around times, with some pressed into service up to three times.

This special collection marks a giant leap forward in our understanding of the Martian system. It reaches across disciplines, will have an immediate impact on broader Mars and solar system sciences, and will be widely read for years to come.

—Andrew Dombard, Benoit Lavraud, and W. K. Peterson, Editors, Geophysical Research Letters, email: [email protected]; and Noah Diffenbaugh, Editor in Chief, Geophysical Research Letters