Glowing Night Clouds May Be An Unexpected Side Effect Of Rocket Launch

Space launches, particularly early morning space launches, cause spectacular glowing clouds to appear in new places, according to new research published in the journal Advancing Earth and Space Science.

About 50 miles (80 kilometers) above the ground floats the tallest clouds in Earth’s atmosphere. Called noctilucent, mesosphere, or polar mesosphere clouds, these crystallized pools of water vapor are high enough to reflect sunlight, even after sunset or even before sunrise.

Because of their position in the upper atmosphere, when they are present at the right time, noctilucent clouds (i.e. “night rays”) sparkle with otherworldly light. They can make the sky at dusk or dawn look like the surface of the sea on a clear day — silvery ripples of light between patches of darkness.

“You see it for about 30 minutes to an hour and a half after sunset, or before sunrise,” Cora Randall, an atmospheric scientist at the University of Colorado, Boulder, and one of the researchers on the new study, said in the video. call with Gizmodo. “And that’s because they’re so thin, the clouds are so thin. You can only see them when the sun shines from them and it’s dark where you stand.”

And emissions from rocket launches, which pump cloud fuel (i.e. water vapor) directly into the mesosphere, likely make this unique formation a more common sight. The launch that occurred at the Kennedy Space Center in Cape Canaveral, Florida, can be correlated with the formation of a noctilucent cloud thousands of miles away and days later.

Usually, noctilucent clouds are not visible because they form most often over the poles and occur during summer in every hemisphere; The season for noctilucents is from mid-May to August in the North and from mid-November to February in the South. The poles never darken during the summer, so noctilucent clouds tend to be swept away by the ever-present sunlight.

However, in recent decades, more noctilucent clouds have been observed at the so-called “middle latitudes,” further from the poles — as far south as California and Colorado. “We’ve noticed that they’re getting brighter and more frequent, basically over the last 50 years or so,” Randall said. Scientists hypothesize that climate change or the solar cycle is to blame.

For the new study, Randall and his fellow researchers collected data in the clouds between 2007 and 2021, collected by NASA’s Aeronomy of Ice in the Mesosphere (AIM) satellite. They focused their attention on latitudes north of between 56 and 60 degrees (a narrow line bordering Bergen, Norway, to the north and Edinburgh, Scotland, to the south), because the median data are the most reliable. What they found was that the clouds did not appear to be following the apparent trend.

Instead, they note that mid-latitude noctilucent clouds vary widely, frequently appearing at some times but not at others. Surprisingly, that year-to-year variability closely followed the frequency of early morning rocket launches, based on data from NASA’s Aeronomy of Ice in the Mesosphere (AIM) satellite.

The researchers also observed that, in the morning, atmospheric winds rapidly carried particles in the mesosphere to the poles, which was in harmony with the observed rocket/noctilucent cloud relationship. The theory is that water vapor from rocket launch emissions is pulled north by winds into areas of the upper atmosphere that are cold enough to form glowing clouds.

Previous case studies have linked noctilucent clouds to Space Shuttle launch emissions. However, this is the first study to show that much smaller rockets seem to have an effect. “The shuttle is, of course, huge compared to some of these other transport vehicles,” said Michael Stevens, an astrophysicist at the Naval Research Laboratory and one of the authors of the recent paper. “So the fact that all the smaller vehicles are contributing, not only contributing, but actually kind of driving [year-to-year cloud] variability, that’s a bit surprising. We didn’t expect that,” he said.

Though it might not just be a rocket. Other factors may still influence the appearance of noctilucent clouds. Climate change, Randall details, will almost certainly still play a role, even if the data set he and his colleagues analyzed doesn’t pick up a clear signal. “There is no question in my mind that anthropogenic activity affects clouds. It’s more about how big it is quantitatively,” he explained.

Interestingly, the relationship between volcanic eruptions and mesospheric clouds has been thought to exist for more than a century. The first known example of a noctilucent cloud sighting was in 1885, two years after the eruption of Krakatoa.

But having a clearer picture of the effects of rocket launches could offer a clearer picture of all the ways humans are changing our planet. Apart from being beautiful to look at, noctilucent clouds don’t have much of a known impact on Earth. Rather, their importance is as a potential indicator of human-caused change.

The mesosphere, and the clouds that appear within it, are very sensitive to small shifts. If we better understand the impact that, say, rockets have, we can use that knowledge to accurately assess the effects of larger atmospheric changes such as massive greenhouse gas emissions, Randall and Stevens said.

Examining noctilucent clouds is also, at its core, a basic expression of human curiosity. “The fact that they became more and more common in the late 20th century and into the 21st century has attracted the interest of many scientists. We want to know why this happened,” Stevens said. For decades, it was a mystery. Now, that’s a little less than one. If you look up at the sky at dusk or dawn and see a shining sea of ​​sky, know that a rocket may have made clouds.

Again: Rocket Launches Could Pollute Our Atmosphere in New and Unexpected Ways.

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