If we ever set foot on the southern hemisphere of Mars, our first Martians might be in for an azure light show (simulated above). Mars has almost all the same astronomical phenomena as we see on Earth, only they look totally different. That includes auroras.
An international team of scientists from NASA, the Institute of Planetology and Astrophysics of Grenoble, the European Space Agency, and Aalto University in Finland recently predicted that auroras can be seen on Mars. The first data came from the SPICAM imaging instrument on ESA’s Mars Express satellite, which saw auroras from space in 2005, findings that were confirmed in March of this year by NASA’s MAVEN mission.
Auroras, like the famous aurora borealis, are caused by charged particles from the Sun interacting with a planet’s magnetic field. As these particles enter the atmosphere, they excite atoms and molecules, and as they release energy to “calm down,” the particles produce light. On Earth, we see auroras as green and red with some occasional blue-purple hues in the mix.
But Mars doesn’t have much of an atmosphere or a magnetic field; it’s so small the solar wind has all but stripped both entirely away. So how can Mars have any kind of night lights?
It’s true that Mars’ global magnetic field essentially shut down about 3.5 billion years ago, but the planet still has smaller, localized magnetic fields that are about 3,000 times less powerful than the Earth’s. They’re called crustal magnetic anomalies, and they’re rooted in Mars’ surface, predominantly in the southern hemisphere — the south is far higher and more rugged than the northern half of the planet.
The Earth’s magnetic field is supported by an internal dynamo of spinning metal. We know Mars had a magnetic field at one point, so it also likely had an internal dynamo that has since shut down. That means any rocks forming during the time of an active dynamo would be magnetized, and so the rocky southern hemisphere is more magnetized than the northern hemisphere. Rocks formed after the dynamo shut down are similarly not magnetized. But that’s only part of the story. Scientists have predicted, through computer models, that if Mars’ northern hemisphere core-mantle boundary was hotter than the southern equivalent, only this latter half would be strongly magnetized.
Either way, it’s consistent with these theories that Martian auroras are only predicted in the southern hemisphere. And astronauts ambling along the planet’s red soil would look up to see predominantly blue light with some red and green hues.
IMAGES: D. Bernard/IPAG — CNRS; NASA/JPL-Caltech/MSSS and CSW/DB