Solar storms have blasted much of Mars's tenuous atmosphere into space over billions of years, making the planet the barren world it is today.

Credit: NASA/JPL-Caltech

A series of papers has outlined the first results from NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, which has been orbiting Mars since September 2014. In one paper, Bruce Jakosky of the University of Colorado Boulder and his colleagues report MAVEN data showing that when protons and electrons from a solar eruption slammed into the planet in March 2015, they increased the rate at which Mars loses its atmosphere by roughly an order of magnitude.

A second paper concludes that only about 10% of the atmospheric particles that leave Mars are recaptured by its gravitational pull; the rest are lost to space permanently, find David Brain of the University of Colorado Boulder and his co-workers.

And when MAVEN flew within 130 kilometres of the Martian surface, it discovered new populations of charged and neutral particles, including oxygen, nitrogen and carbon dioxide. These were found at unexpectedly low altitudes in the Martian atmosphere, say Stephen Bougher of the University of Michigan in Ann Arbor and his team in a third paper. Together, the findings show that Mars's atmosphere is more complex and dynamic than scientists had thought.

Science (2015); Geophys. Res. Lett. (2015); Science (2015)