Looking at photos of Earth from space can be quite remarkable. Not only does it give us a sense of perspective and make us reflect on the triviality of our current problems, but it also allows us to appreciate the beauty of our planet. Recently, NASA shared a breathtaking image taken from the International Space Station (ISS). The photo captures a golden glow surrounding the Earth’s horizon. Is it a sunset or a sunrise? Well, it’s actually neither, and let’s delve into the details while we admire this image.
NASA released this image from the ISS, showcasing the Earth’s atmospheric glow along with a starry sky. According to NASA, the picture was taken when the ISS was positioned 258 miles above the Pacific Ocean, northeast of Papua New Guinea. In the photograph, we can spot the Nauka science module and the Prichal docking module, both from Roscosmos, situated on the left.
Now, let’s delve into the golden glow seen around the Earth. This glow is known as airglow and it is a faint natural light emanating from the upper atmosphere, typically found between 70 and 400 kilometers above the Earth’s surface. This light occurs when sunlight interacts with atoms and molecules in the upper atmosphere, causing them to become excited and reach higher energy levels. As these particles return to their original state, they emit energy in the form of light, creating the phenomenon known as airglow.
Airglow can take on different colors, but the golden-yellow shade is the most common. It is primarily caused by excited sodium atoms. However, airglow can also appear red or green, resulting from excited oxygen and hydroxyl molecules, or nitrogen molecules, respectively.
The Earth’s night glow is usually quite dim, but it can be observed at higher altitudes. Astronauts and cameras aboard the ISS have the most advantageous perspective to witness this spectacle. It’s interesting to note that Earth is not the only celestial body that glows; Mars also exhibits a similar phenomenon. In late 2023, the ExoMars Trace Gas Orbiter, operated by the European Space Agency (ESA), captured Mars’ green glow, providing us with even more mesmerizing images to admire.