Noctilucent clouds shimmer in summer sky, with a possible boost from rockets
They glow in twilight, hover 50 miles above the ground, and may be forming more often thanks to rockets blasting into orbit.
Noctilucent clouds or night clouds over St Mary's Lighthouse in Whitley Bay, North Tyneside, taken at 01.45 am on Friday July 5, 2024. (Photo by Owen Humphreys/PA Images via Getty Images)
Summer brings the shortest nights of the year and the rare chance to see clouds with origins in outer space.
Known as noctilucent clouds, these shimmering, electric-blue formations hover roughly 50 miles above Earth, far higher than typical clouds. They are most commonly seen between late June and early August, when sunlight shines at just the right angle to illuminate the clouds.
"They are thought to form when water vapor condenses around ‘seeds’ of dust from vaporized meteorites," NASA explained.
Noctilucent clouds, also known as night-shining clouds, are reflected in the water of the Neris River in Vilnius, Lithuania. This cloud-like phenomenon in the upper atmosphere layers, at heights of 70-90 kilometers, from the ground is only visible during astronomical twilight. (Photo by Yauhen Yerchak/SOPA Images/LightRocket via Getty Images)
They're most common at high latitudes, making them more frequently visible in regions like Canada and parts of Europe. "Your best opportunity to spot noctilucent clouds occurs from about half an hour to two hours after sunset during the summer months," NASA said.
However, there is one more way for people to see noctilucent clouds, even when it's not summertime.
Rocket-fueled clouds
While most noctilucent clouds have natural origins, there's growing evidence that rocket launches can create or enhance them. During some early morning launches, rocket exhaust is carried into the upper atmosphere.
“Winds can easily carry the exhaust from morning rocket launches at lower latitudes, such as from Florida or southern California, toward the poles,” NASA explained. “There, the rocket exhaust turns into ice crystals and descends to form clouds.”
A San Diego resident captured a bright blue streak in the sky overhead during a recent SpaceX Starlink launch on Feb. 10.
These human-made noctilucent clouds have been documented since the days of the Space Shuttle but are now most commonly linked to SpaceX launches. A recent analysis found a noticeable uptick in noctilucent cloud sightings after launches that occur between 11 p.m. and 10 a.m. local time.
“This research, relating changes in mesospheric cloud frequency to rocket launches, helps us to better understand the observed long-term changes in the occurrence of these clouds,” said NASA Heliophysics Program Scientist John McCormack.
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