AOctilucent clouds are a rare and special sight. Visible only at latitudes between 45° and 80°, these shimmering fluffy silver-blue clouds can occasionally be seen high in the sky on a clear summer night. But in recent decades, they’ve appeared more frequently, and now a new study has revealed that space launches help spawn them.
Consisting of very thin sheets of ice crystals, nocturnal – “glow at night” – clouds only form under special circumstances. High up in the dry mesosphere, about 80 miles (80 km) above the Earth’s surface, the clouds need dust particles, moisture and very cold temperatures to form. Explosive volcanic eruptions sometimes produce these ingredients, and so do meteor showers. In the 19th century, nocturnal clouds were seen only once every few decades, but now they can be seen several times each summer, with July being the most likely month. So what changed?
Write in the journal Earth and Space Science, researchers show a strong correlation between summer rocket launches and the frequency of nocturnal clouds. Each launch spews out tons of water vapor which, if the wind blows the right way, condenses and helps cause cloud formation. Along with rocket launches, climate change is also playing a role, making nocturnal clouds a more frequent feature of the night sky.
