Sometimes at latitudes between 50 and 70 degrees, when the sun illuminates the upper layers of the atmosphere from below the horizon and leaves the rest in the cold darkness, you can see one of the most subtle and beautiful phenomena on Earth: noctilucent clouds, also known as night-shining clouds.
These are rare, bright, elusive clouds that are 50 miles above the ground. In essence, they're a meteorological phenomenon that resemble the pattern of the capillaries of a living being seen in an angiography, which is an X-ray used to examine blood vessels.
This phenomenon occurs in summer, though not always. In 2024, for example, experts weren’t expecting to see night-shining clouds, but something strange is happening in the mesosphere. Understandably, scientists are intrigued.
What exactly are noctilucent clouds? According to the Royal Museums Greenwich, noctilucent clouds get their name from the fact that they shine at night. During twilight or just before dawn, the sun’s rays illuminate these clouds and give them their characteristic bright white color with a slightly bluish tint.
They’re also the clouds at the highest altitude that exist on our planet. As such, they’ve been a major enigma for meteorologists for almost a century and a half. Scientists still don’t fully understand the mechanism that forms them. However, they do have their suspicions.
What’s behind these weird clouds? Some scientists believe that noctilucent clouds form when scarce water vapor reaches high altitudes and condenses around microscopic particles of dust, which could come from meteorites or comets disintegrating in the Earth’s atmosphere.
Traditionally, experts believed that these clouds couldn’t be seen during periods of high solar activity because the radiation would melt the meteor debris and prevent the clouds from forming.
However, despite the peak of solar cycle 25 in 2024, there have been numerous sightings of night-shining clouds, even at low latitudes in Ireland, England, and France. Experts find this situation very unusual.
What’s happening? According to meteorologist Francisco Martín León, one potential explanation is that the Hunga Tonga volcano eruption on January 15, 2022, injected a significant amount of water vapor into the mesosphere at a height of more than 6 miles, which translates to about 150 million metric tons of water vapor. A large part of it would still be in the high layers of the atmosphere, potentially leading to unprecedented levels of moisture in mesosphere.
Some experts believe that the increased moisture in the mesosphere could be compensating for the scarcity of meteorite debris.
And what about SpaceX? But Martín León believes rockets can also be a source of moisture in the mesosphere. Currently, more rockets are being launched than ever before, about four times more than during the previous solar maximum period. No shade to China, but SpaceX is the primary contributor to the increased launches.
In any case, scientists need to understand the mesosphere better. The satellites monitoring Earth must provide them with data regarding the situation up there. Given the combination of climate change, extreme weather events, and intensified competition in space exploration, having this information will be essential.
Image | Martin Koitmäe
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