A NASA balloon has captured rare images from right at the very edge of Earth's atmosphere, where it has been examining a thin group of electric blue clouds with high-powered cameras.
Polar mesospheric clouds (PMCs) form 50 miles above the poles during summer. They're mostly made up of ice crystals and appear like faint lines in the sky.
The clouds are only visible during twilight, when the angle of the sun reflects off them and causes them to shine a bright electric blue or white colour.
Over the course of a five-day mission, a NASA research balloon captured pictures of these clouds in the mesosphere - near to the very edge of space.
It flew from Sweden across the Arctic to Canada using the sophisticated cameras aboard to snap six million high-resolution images which the scientists are now analysing.
"From what we've seen so far, we expect to have a really spectacular dataset from this mission," said Dave Fritts, the mission's principal investigator.
Mr Fritts, of the PMC Turbo mission at Global Atmospheric Technologies and Sciences in Boulder, added that the team hoped the dataset would provide "new insights into these complex dynamics".
Atmospheric motions, such as airflow over mountains or the motions caused by thunderstorms, can cause disturbances in the atmosphere which are generated through something called gravity waves.
Gravity waves are misnamed - they're not actual waves in the fabric of space-time - but in many ways they are just as curious.
They can't be seen directly, but their effects on PMCs are very visible - especially to a balloon in the mesosphere.
The kinds of gravity waves the researchers were examining are caused by the convecting and uplifting of masses of air and play a major role in transferring energy from the lower atmosphere up to the mesosphere.
"This is the first time we've been able to visualise the flow of energy from larger gravity waves to smaller flow instabilities and turbulence in the upper atmosphere," said Mr Fritts.
"At these altitudes you can literally see the gravity waves breaking - like ocean waves on the beach - and cascading to turbulence."
The scientific instruments aboard the balloon were successfully recovered from the Canadian Arctic, and NASA expects the recovered instruments will contribute to future missions.
Scientists want to understand the processes of matter in near-Earth space, including how matter there interacts with Earth's atmosphere and weather.