Constellation Urion: when astronaut pee became a UFO

We’ve all been there. You're driving down a long, deserted country road with no rest stop in sight. Sooner or later, nature calls — and you pull over, duck behind some bushes, and hope to finish before anyone passes by. The last thing you expect when leaving the scene is for the evidence to follow you, revealing your secrets to the world. Yet, that is exactly what happens in space. A spacecraft can't stop to dispose of waste, so anything that exits the craft will follow it until the difference in velocities eventually separates them.

Fig. 1. An artistic depiction of a spacecraft encircled by frozen droplets.

When nature calls in orbit. In the early days of space flight, there were no fancy recycling systems or closed-loop plumbing on board. Astronauts aboard missions like Gemini and Apollo had a simple, if inelegant, solution: they vented urine directly into space. As soon as the liquid left the spacecraft, it met the vacuum of space and instantly froze. Millions of tiny ice crystals formed, spreading out in a glittering cloud that drifted alongside the ship. In sunlight, the frozen droplets caught and reflected light in all directions, creating a shimmering halo that looked, for all the world, like a miniature galaxy. It was, quite literally, the most beautiful bathroom break in history. 

The "Constellation Urion". Astronaut Wally Schirra, ever the joker, once called it "Constellation Urion" after seeing one of these sparkling displays during the Gemini missions. And Apollo 9 astronaut Rusty Schweickart described it later as "one of the most beautiful sights in orbit... a spray of sparklers at sunset. "The sight wasn't just funny, it was genuinely mesmerising. During an Apollo urine dump, the crew would time the venting near orbital sunrise or sunset, when sunlight hit the frozen cloid at just the right angle. For a few minutes, the ship would be surrounded by what looked like a swarm of diamonds.

Fig. 2. NASA astronauts: Wally Schirra (left) and Rusty Schweickart (right)

Science in the sparkle. Behind the poetry was some practical physics. In orbital microgravity, liquids are weightless. They don't fall; they flow. When exposed to the vacuum of space, water (and, yes, urine) rapidly boils away and freezes simultaneously, forming a trail of fine, reflective ice crystals. These particles gradually disperse, but in the meantime, they can hang around the spacecraft, even reflecting sunlight toward the windows. Mission controllers, meanwhile, had to keep track of these ventings, not for hygiene, but because the escaping mass could subtly alter the spacecraft’s trajectory. Even bodily fluids could knock a billion-dollar rocket off course, if only by a fraction.

From dump to drink. Fast-forward to today, and things have come considerably more refined. On the International Space Station, nothing is wasted. Modern life-support systems can reclaim and purify urine into clean drinking water, a process astronauts wryly summarize as: "Yesterday's coffee becomes tomorrow's coffee." The sparkling clouds are gone, but their legend remains – a small, glittering reminder of how space travel turns even the most mundane human needs into something extraordinary.

When astronomers mistook pee for a UFO. On more than one occasion, skywatchers on Earth have spotted these glittering plumes from orbiting spacecraft and mistaken them for something mysterious: a strange glow, a comet fragment, or even a visiting spaceship from beyond the stars. The sight set off a flurry of excited reports and speculation among amateur astronomers. Was it space debris? A meteor shower? A new phenomenon in the upper atmosphere? Little did they know, the glowing visitor they admired wasn't an alien at all. Its origins were much more mundane and down-to-earth. A glittering cloud silently twinkling across the night sky was not a UFO but an astronaut's urine frozen in the near absolute zero temperatures of outer space.