ISS captures two magical Earth phenomena in one image, See photo here

NASA recently posted a pre-dawn picture of Earth taken by an Expedition 62 crew member on the International Space Station (ISS). This image was taken in March 2020. According to NASA, this stunning image was taken when the ISS was flying south of the Alaskan Peninsula. The fantastic colours seen in the picture are particles in Earth's upper atmosphere which are interacting in different ways. This resulted in two entirely different atmospheric phenomena getting captured in one picture.

Source: NASA

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Which two phenomena were captured by the ISS?

The Aurora Lights

The first and probably one of the most recognisable phenomenon on Earth is the Aurora lights, also known as the northern lights. Aurora can be spotted on the left side of this stunning image. One can see a glowing green light with a red-tip. 

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Aurora occurs in northern Scandinavian Islands, the southern tip of Greenland and also continues over to northern Canada and Alaska. The marvellous light show can also be seen in the northern coast of Siberia. Aurora typically occurs when charged particles from the solar wind collide with Earth's magnetosphere, which is a kind of protective cloak around the earth. The magnetically charged particles present in this region are mixed with atmospheric gases such as oxygen and nitrogen, and they create the striking colours known as the Aurora.

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Airglow

The Aurora lights form only one part of this shot taken by the ISS. On the right side of the above image, one can see the yellowish-red band of light, above the curve of Earth. According to a NASA report, this is called 'airglow'. Airglows are typically more subtle than the aurora.

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According to NASA, in order to understand Airglow, one needs to remember that the night sky is never completely dark. Even if we extract all the light pollution, starlight, and diffuse sunlight, the atoms still produce 'emissions'. Atoms are in an excited state which causes them to produce these emissions. For instance, Oxygen molecules that have been broken apart during the day recombine and release their extra energy as photons at night. Nitrogen molecules react with the oxygen molecules and contribute to this pre-dawn glow as well.

The bright photons released as a result of this appear green. Hence, one can see the presence of slight greenish-yellow colour in the lower layers of the Earth in the picture. This is typically 80-100 km above Earth’s surface. This layer is called the sodium layer, as many meteors break up in this layer of the atmosphere, and release sodium atoms into the air.