July 1, 2022: Something unexpected just happened in the mesosphere. As June came to an end, NASA’s AIM spacecraft detected a sharp increase in the frequency of noctilucent clouds (NLCs), the most in 15 years:
“In the last couple of days we saw a huge spike in the clouds,” says Cora Randall, a professor at the University of Colorado Boulder. Randall works with AIM data and she prepared the plot, above.
NLCs are Earth’s highest clouds. Seeded by meteoroids, they float at the edge of space more than 80 km above the ground. NLCs form when summertime wisps of water vapor rise up to the mesosphere, allowing water to crystallize around specks of meteor smoke.
Oliver Schwenn witnessed the outbreak on June 30th from Aarhus, Denmark:
“I photographed the display shortly before midnight,” says Schwenn. “The clouds were shining brightly in the night sky.”
What’s causing this? It could be SpaceX.
“We’re speculating that the spike might be due to extra water vapor transported to higher latitudes from rocket launches,” says Randall. “But much more quantitative analysis would be required to confirm that or not.”
The timing makes sense. It takes about 10 days for water vapor from rocket engines to waft up to the mesosphere. This takes us back to SpaceX’s launch of the Globalstar satellite on June 19th, which caused a number of remarkable phenomena in the sky due to the extra burn time of its second-stage engine. Noctilucent clouds may be yet another by-product of that unusual launch.
Noctilucent clouds are normally a polar phenomenon. However, since the outburst began we have received reports of NLCs from as far south as Washington State and Oregon. Look for the clouds, ripply and electric-blue, just after sunset.