A bluish-green vapour cloud hung in the atmosphere over the East Coast shortly after 7:07 pm on Oct. 7, following a successful NASA launch of the Black Brant IX suborbital rocket from Wallops Island, Virginia.
Minutes after launch, the rocket released four bursts that contained mixtures of the chemical elements barium and strontium — the same chemicals that give fireworks their bright colours.
Aside from the main mission of the launch, which was to test one of the rocket’s new motors, the secondary experiment involved ejecting a colourful package of vapour tracers that, since the 1950s, have been used to help scientists visualise how particles move around in the upper atmosphere.
Barium is a soft and shiny alkaline earth metal, and can be found in fluorescent lamps, paints, bricks, tiles, glass, and rubber. Strontium has similar physical and chemical properties to barium, but is much more expensive.
Observers took to social media to document the launch and the cloud. Here are a few of our favourite images.
Business Insider Emails & Alerts
Site highlights each day to your inbox.