A NASA-funded study is giving scientists insight into how “night-shining clouds” form within the upper atmosphere — and therefore the role that growing space traffic plays in phenomenon.
Scientists have known about these high flying clouds since a min. of the late 1800s — well before the space exploration age that launched in 1957. Newer research, however, shows that these clouds tend to make in high-altitude areas with abundant water vapour , like what’s produced after modern-day rocket launches.
The polar mesospheric clouds (PMCs), because the clouds are formally called, are collections of ice crystals usually found over the north or south poles during the late spring and summer. They’re easiest to identify at twilight when the sun shines on them from slightly below Earth’s horizon.
“What has attracted more of interest within these clouds is their sensitivity — they’re occurring just on the end point of viability in the upper atmosphere, where it’s incredibly dry and incredibly cold,” lead author Richard Collins, a space physicist at the University of Alaska, Fairbanks, said during a statement. “They’re a really sensitive indicator of changes within the upper atmosphere — changes in temperature and/or changes in water vapour.”
Collins and his team followed the origin story of PMCs using NASA’s Super Soaker mission, which used alittle suborbital rocket that flew to space from Alaska. Water vapour from such launches, the study suggests, can lower the temperature within the immediate region and make a shiny cloud. Team members found this even happens in January during the toughest conditions within the Arctic — when PMCs don’t typically form.
“We wanted to confirm to avoid mixing artificially created and present PMCs. That way, we might be confident that any PMC we observed was due to the Super Soaker experiment,” Irfan Azeem, a space physicist at Astra in Colorado and PI (principle investigator) of the Super Soaker mission, said within the same statement.
After the rocket launched on Jan. 26, 2018, from the Poker Flat research range near Fairbanks, it flew to 53 miles (85 kilometers) in altitude and deliberately released 485 lbs. (219 kilograms) of water packed into a canister. Just 18 sec later, ground-based laser radar picked up the signature of a PMC.
The team also put their results into a model to estimate how PMCs formed. The model suggested that the water from Super Soaker must have cooled the air dramatically, by about 45 degrees Fahrenheit (25 degrees Celsius). “We do not have direct temperature measurements of the cloud, but we might infer that temperature change totally based on what we expect is required for the cloud to make ,” Collins said.
While this experiment threw water vapour into the air with a canister, water vapour may be a common byproduct of satellites and rocket launches — like with the spacecraft that flew from NASA’s Kennedy Space Center between 1981 and 2011. One launch of the spacecraft spurred 20% of PMC ice mass noticed in a season, the team members said in their statement.
“As the water vapour freezes, it turns into ice crystals. But those ice crystals absorb heat even better than water in vapor form. because the ice crystals heat up, they eventually sublimate back to vapor, and therefore the cycle repeats,” NASA added within the statement.
This research first reported in the Journal of Geophysical Research: Space Physics