Mars and Airglow.
This is going to be a slightly nerdy post. I have been fascinated by the colours of airglow that my camera has captured on this trip to Ladakh, and have been researching their origin! According to wikipedia, Airglow is caused by chemiluminescence in the atmosphere, which is essentially the release of light through chemical reaction. I wanted to know more, so over the last few days, I've been reading articles written by nasa scientists and other astronomy experts.
It turns out, that there is a direct link between the Auroras seen around the north and south poles and the Airglow that I've saw. They are caused by the same phenomena! By the exact same chemical reactions!
The green Airglow originates from electronic emission lines of Oxygen, between 90 to 100 km above sea level. Red can come from a different electronic emission line of Oxygen at altitudes of 150 to 300 km or from Hydroxyl molecules (OH) at altitudes around 90 km. Yellow Airglow comes from Sodium at 92 km.
Cosmic rays and solar wind excite the atmosphere, causing these reactions at a very low intensities. They occur all around the globe. Around the poles, the magnetic field of our planet, traps electrons and protons from the solar wind, making these chemical reactions much more pronounced! This is the reason why Auroras are only seen around the north and south poles.
In this image, the bright orange "star" on the top is actually Mars. The rising moon illuminates the snowy peaks while bands of green and faint red grace the star studded sky.