An astronaut captured two 'blue blobs' from the ISS. Here's everything to know

What can be seen in the image?

The image was captured when the ISS was flying above Southeast Asia, and the limb of the Earth is seen as the orange-yellow halo parallel to the curvature of the Earth. The image captures areas of China, Thailand, Vietnam, and Laos, as well as the Gulf of Thailand and the South China Sea.

The ring of lights in the central part of the image is the Hainan island, the southernmost province of China, which millions of years ago was connected to the Chinese mainland. Over the years, the Hainan Straight was formed as the landmass drifted apart, and today it sits 12 miles (20 km) from the mainland.

The night lights are a representation of the population density of the region, with the landlocked country of Laos showing up as a strip of darkness.

At the bottom of the image is a big blob of lightning occurring somewhere over the Gulf of Thailand. The cloud cover, which usually hides lightning from the ISS, seems to have thinned down just enough for the lightning strike to be captured by the 28 mm lens of the Nikon D5, captured as a ring, illuminated in blue.

Why is it blue?

Near the right end of the image is another blob of blue, which is not another bolt of lightning in the South China sea but the light from the Moon. As Live Science reported, the Moon was likely at an orientation where the light it was reflecting from the Sun passed through the Earth's atmosphere scattering off some tiny particles.

When visible light interacts with particles in the atmosphere, the latter can cause them to scatter. Since blue is the shortest wavelength, it is likely to be scattered the most and is the reason the sky also appears blue during the day.