The latest results from the MAVEN Mars Orbiter show that global magnetic fields are critical to preserving the planetary atmosphere and protecting living environments from destructive emissions from parent stars. Particles of the solar wind, consisting mainly of protons and electrons, apparently can and do deprive many rocky planets of most of their atmospheres.
According to the MAVEN mission, about 3.5 billion years ago, the wind of our Sun stripped the Red Planet of up to 80-90% of its atmosphere. The earth is more fortunate. But for astrobiologists, the question remains: to what extent do planets have a stable global magnetic field? And how well are these magnetic fields retained, especially in close orbits around active red dwarf stars?
Mission chief specialist Bruce Jakosky believes that if the planet does not have a magnetic field, a relatively rapid loss of atmosphere can be expected with obvious consequences for existing life. Loss of atmosphere will also depend on the intensity of the star and stellar wind over time, the size of the planet and, to a lesser extent, the composition of the atmosphere.
Dave Brain, a planetary scientist at the University of Colorado at Boulder, noted: "Some exoplanets are subject to such harsh stellar conditions that they should not have retained an atmosphere at all - regardless of whether the planet has a magnetic field."