This is why Mars's sky turned green this week
What's the story
Mars, the fourth planet from the Sun, witnessed a spectacular display of auroras this week. The celestial event was triggered by an X2.7 solar flare on May 14 and a subsequent coronal mass ejection (CME), that released a cloud of charged particles toward Mars. According to Spaceweather.com, the particles interacted with Mars's atmosphere and ultimately turned it green.
Formation
How auroras form on Mars
Auroras are not emitted by the Sun but are the result of charged particles interacting with a planet's magnetic field and atmosphere. Unlike Earth, Mars has a weak magnetic field and a thin atmosphere, which leads to unique aurora types. Specifically, solar energetic particle auroras occur when super-energetic particles from the Sun strike the Martian atmosphere, causing it to glow.
Detection
How Perseverance detected green auroras
Previously, Martian auroras were only observed at ultraviolet wavelengths by orbiting spacecraft. However, the Perseverance rover detected the green auroras using visible light cameras. Elise Knutsen, a postdoctoral researcher at the University of Oslo in Norway and lead author of a paper published in Science Advances, said they had to select an appropriate CME for this aurora detection.
Cycle
Sun shifting from solar maximum
The Sun is currently moving away from the peak of its approximately 11-year solar cycle, called the solar maximum. This phase is marked by increased magnetic activity. NASA and NOAA's Solar Cycle 25 Prediction Panel had announced the arrival of this period in October 2024.