Blue Aurorae in Mars’ Sky Visible to the Naked Eye

NASA | MAY 31, 2015

Visible Martian aurorae seemed possible after the SPICAM imaging instrument on-board the ESA satellite Mars Express spotted aurorae from space in 2005. Those observations were confirmed in March 2015 by the NASA-led MAVEN mission.

The Planeterella sphere simulates a magnetized planet with an atmosphere of CO2 and bombarded by the solar wind. Blue aurorae develop according to its magnetic field configuration. Image credits: D. Bernard/IPAG — CNRS/NASA

Through laboratory experiments and a physical numerical model developed at NASA and IPAG, the study shows that, on Mars, aurorae also occur in the visible range. The most intense color is deep blue. As on Earth, green and red colors are also present. Several times during a solar cycle, after intense solar eruptions, these lights are bright enough to be seen with the naked eye.

Aurorae occur when charged solar particles reach local magnetic field lines, where they enter the planetary atmosphere and excite its atoms and molecules. As they deactivate, the particles produce light emission. On Earth, aurorae are essentially green or red (excitation of atomic oxygen), but even blue-purple (excitation of ionized molecular nitrogen) can be seen.

At the beginning of Mars’ existence and up until 3.5 billion years ago, the red planet hosted a global magnetic field. Although this global field somehow shut down, local spots of increased magnetic fields, called crustal magnetic anomalies, still remain in Mars' surface. These anomalies are concentrated in the southern hemisphere, where aurorae are predicted to occur.

It is predicted that an astronaut walking on the red soil of the planet could look up to see the southern night sky glow blue, with red and green hues.

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