Polar Mesospheric Clouds: Unique perspective of shimmering clouds

During one of the 16 sunsets visible from the International Space Station each day, this unique perspective of polar mesospheric clouds was captured in July.

Also known as noctilucent clouds, these are the highest forming clouds on Earth, appearing at altitudes of more than 50 miles from the ground. This latest image was captured over the Mediterranean Sea.

Their wispy appearance is thanks to the ice crystals which form in the freezing cold mesosphere, which sees temperatures reaching as low as -200 degrees.

Best seen at dawn and dusk, these clouds have gradually become more visible to those in the mid-latitudes.

While historically they are seen at higher latitudes beyond 50° north or south, those captured by the ISS were over the Mediterranean at a latitude of 40 degrees north latitude.

While it is not understood why they are beginning to appear at these lower latitudes, two prevailing theories suggest that increased humidity in the mesosphere or exhaust plumes from launching space vehicles could play a role.

Noctilucent clouds can be seen from the extreme northern U.S. during the summer months between July and August.

As they form at such extreme altitudes, they have no effect on weather systems impacting the ground, and can often be obscured by lower-forming clouds.

If you have ever seen, or manage to capture late-forming noctilucent clouds, we would love to see your pictures! Simply tap the image icon in the app or use our dedicated uploader to submit.