A solar event on September 11, 2017 sparked a global aurora on the Red Planet more than 25 times brighter than any previously seen by NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft. The event also produced radiation levels on the Martian surface more than double any previously measured by NASA’s Curiosity rover.
The Sun is always emitting a continuous stream of charged particles, mainly electrons and protons.
Occasionally, eruptions called coronal mass ejections occur, with higher density, energy and speed of the ejected particles.
These events vary in strength. Strong ones cause dramatic aurora displays on Earth, and very strong ones can disrupt communications. Some coronal mass ejections, such as the September 11 event, are broad enough in extent to affect planets in quite different directions from the Sun.
“When a solar storm hits the Martian atmosphere, it can trigger auroras that light up the whole planet in UV light. The recent one lit up Mars like a light bulb,” said Dr. Sonal Jain, a member of MAVEN’s Imaging Ultraviolet Spectrograph instrument team and a researcher at the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics.
“An aurora on Mars can envelope the entire planet because Mars has no strong magnetic field like Earth’s to concentrate the aurora near polar regions.”
“The energetic particles from the Sun also can be absorbed by the upper atmosphere, increasing its temperature and causing it to swell up.”