New Delhi, March 1: When imagining Earth from space, many envision the beautiful images of the “blue planet.” However, a remarkable sight emerges when viewed from the International Space Station (ISS), located in low Earth orbit. At an altitude of just 300 miles, vibrant layers of red, green, purple, and yellow light can be seen in the upper atmosphere. This phenomenon is known scientifically as “airglow.” It represents Earth’s natural aura, preventing the night sky from becoming completely dark and showcasing the complex processes within our atmosphere.
According to NASA, airglow occurs when atoms and molecules in the upper atmosphere become more active due to sunlight. They release light in the form of photons to shed their excess energy. This process is similar to auroras, but while auroras are created by high-energy particles from solar winds, airglow derives energy from the sun’s normal daily light. Occasionally, ionized atoms also produce light by colliding with free electrons.
The night sky is never completely black. Even without light pollution, moonlight, or stars, a faint colorful glow persists, which is airglow. This glow accounts for about one-tenth of the total light from all stars. From space, it appears as a luminous bubble surrounding the Earth, extending from 50 to 400 miles high, where the ionosphere is located. This region is also where our GPS signals travel and where astronauts navigate.
The colors of airglow originate from different gases. The brightest green light is produced by oxygen atoms, while red and other colors result from various reactions involving nitrogen and oxygen. Some colors exist in ultraviolet and infrared wavelengths, which are not visible to the naked eye. The thinness of the upper atmosphere allows atoms to remain excited longer without colliding, thus emitting light. In the denser lower atmosphere, collisions are more frequent, resulting in less light production. This glow continuously changes, influenced by both solar energy and Earth’s weather.
Airglow serves as a marker for changes in the ionosphere. Just as smoke in the air indicates wind patterns, the movement and presence of airglow particles provide information about temperature, density, and structure, aiding in understanding the relationship between space weather and Earth’s climate.
Scientists are continuously studying this beautiful phenomenon as it is a crucial means of understanding the connection between space and Earth’s weather. Images taken from the ISS clearly show these colorful bands, which help scientists monitor activities in the upper atmosphere.
