Lichtende nachtwolken zijn wolken die voorkomen op ongeveer 75 tot 85 kilometer hoogte, veel hoger dan gewone wolken, die hooguit zo'n 20 kilometer hoogte bereiken. Na zonsondergang weerkaatsen die hoge wolken nog een tijd zonlicht.
DID SPACEX MAKE THESE NOCTILUCENT CLOUDS? Maybe it's just a coincidence. Shortly after midnight on June 24th, people in Europe watched a rocket glide silently overhead. A few hours later, noctilucent clouds (NLCs) filled the sky.
"It was incredible," reports Stanislaw Rokita from Torun, Poland, the hometown of Copernicus. "Silver filaments spread over almost half the horizon and rose all the way to the zenith."
Similar displays were seen in Berlin, Paris and other European cities.
NLCs are a natural phenomenon. They form when summertime wisps of water vapor rise up to the mesosphere (83 km high) and frost specks of meteor smoke. We see them every year during weeks around the summer solstice. This, however, was an unusually bright and widespread display.
Some onlookers wondered if the rocket had anything to do with it. The rocket was SpaceX's Transporter-14 mission, launched the previous evening from California's Vandenberg Space Force Base. Onboard were 70 payloads, including cremated human remains and small surveillance satellites. A fuel dump from the rocket's second stage was widely observed only a few hours before the NLCs appeared.
This picture from Nicolas Rossetto of Jura, France, shows the rocket (inset) trailed by a cloud of discarded propellant:
"This was about 15 minutes past midnight," says Rossetto.
Could Transporter-14 be responsible for the NLCs? Theoretically, yes. Studies show that space traffic does indeed amplify noctilucent clouds. Rocket engines emit water vapor--a key ingredient of NLCs. Moreover, a video of the Transporter-14 launch shows the second stage engine burning through the mesosphere and spewing water exactly where NLCs form.
But there's a problem with this idea. The burn happened over the coast of California, not Europe. To make morning clouds over Paris and Berlin, the water vapor would need to travel 10,000 km in less than 6 hours--*very* unlikely.
The display was probably natural. If so, more NLCs could be in the offing--no rockets required.
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