Very high in the atmosphere of Mars, astronomers have spotted a phenomenon they’ve been hunting for many years: a faint green glow.
The discovery of the green glow in the Mars’ atmosphere will help astronomers better understand the processes that drive airglow, both on our planet and elsewhere. Here is what you should know.
Mars’s Green Glow Examined
Previously, astronomers have only spotted the green glow in one place, on the sky above our planet. Earth’s sky is never entirely dark, not even at night. The molecules in the atmosphere are always undergoing different processes, which trigger them to glow across a spectrum of wavelengths faintly.
The glow is different from aurora since it’s made by the same particles – except it’s much weaker, and the mechanisms behind it are complex. Aurora, for instance, is generated by charged particles from the solar wind, which ionize atmospheric atoms, influencing them to produce whirling lights across the sky.
Airglow, on the other hand, is triggered by the interaction between the atmosphere and the sunlight and falls widely into two categories. There’s the nightglow, that appears when atoms tear apart by solar radiation during the day recombine, discharging their excess energy in the form of photons. Nightglow has previously been spotted on both Mars and Venus, and our planet, too.
What astronomers have now seen in the atmosphere of Mars is dayglow. Such a thing represents a challenging phenomenon due to its faint presence that is very outshone by broad daylight. Astronomers predicted such dayglow in 1979, but Mars orbiters, facing directly at the Martian surface, couldn’t observe it until now.
The Nadir and Occultation for MArs Discovery (NOMAD) device needed to be reoriented to look across the atmosphere towards the Mars’ horizon. From the current position, astronomers realized a series of observations of the Martian atmosphere, at altitudes between 20 and 400 kilometers. More results should be published in the coming months.