A Halo above The Earth's Horizon | International Space Station

A Halo above The Earth's Horizon | International Space Station

An astronaut aboard the International Space Station took this photo while orbiting over the Indian Ocean. The Earth appears black in the lower half of this image, mirroring the darkness of space above. Atmospheric layers span the image, displaying a range of hues. The troposphere generally appears orange and red, the stratosphere is mostly white, and the mesosphere is shades of blue. The Moon, with a shimmering streak-like feature below it, is visible near the top atmospheric layers.

When this photograph was captured on September 4, 2024, the Moon was in the waxing crescent phase. During this phase, only a sliver of the Moon is illuminated by reflected sunlight, visible as the extra-bright white crescent on the Moon’s lower-right edge. Camera settings such as exposure, shutter speed, and aperture increased the visibility of the Moon in this image, giving the impression of a full Moon. 

At the time of this photo, the Moon was positioned behind Earth’s atmosphere relative to the space station. The atmosphere acts like a lens, bending light that passes through it and toward the astronaut’s camera, causing the Moon to appear non-uniform in shape.

Bent, or refracted, light also led to another optical phenomenon in this image. Water vapor that reaches high in the atmosphere can freeze onto tiny dust particles, generating ice crystals in the mesosphere. Light refracted by these ice crystals likely formed the arc-shaped partial lunar halo visible near the Moon.

Image Description: The bottom third of the photo is solid black. It is topped by atmospheric layers of orange, red, white, and blue. The Moon is visible near the top of the blue atmospheric, layer where it fades into the blackness of space. Cradling the Moon on its bottom-right side is an arc-shaped strip of white light. A subtle arc, formed by the bending of light through high-altitude ice crystals, cradles the Moon above the darkened Earth.

Image details: Nikon Z9 digital camera using a focal length of 200 millimeters

Image Credit: NASA's Johnson Space Center
Text Credit: Elysia N. Viengkham, Amentum-JETS II Contract at NASA-JSC
Capture Date: Sept. 4, 2024
Release Date: Aug. 17, 2025

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