Where does astronaut poop go?

The stunning meteor shower  that streaks across the night sky may be caused by something more... organic. Next time you see a shooting star, know this: It could be astronaut poop .

Astronaut Scott Kelly’s body went through some strange changes while he spent a year on the International Space Station with Russian cosmonaut Mikhail Kornienko. The mission was designed to study the effects of long-duration spaceflight and lasted twice as long as the average ISS trip. There was another interesting aspect to the experiment: Scott Kelly would be the test subject in space, while his identical twin brother, astronaut Mark Kelly, would stay on Earth and act as a controller.

When the results from the Twins Study were released, NASA was not disappointed. Scott Kelly’s telomeres grew longer in space, but shortened when he returned to Earth, a potential sign of stress and aging. He had lost 7 percent of his body mass. Bodily fluids equivalent to a 2-liter soda bottle spilled from his lower body to his head and chest. The diversity of bacteria in his stool had plummeted.

During the 2015-2016 mission, NASA also shared some numbers that are sure to concern the hygiene-conscious among us. Kelly drank about 730 liters of water made from recycled urine and sweat, and he passed about 82kg of feces. Of course, astronaut poop can’t just be flushed down the drain, since there are no sewers in space. Instead, it’s dumped out of the station along with other ISS waste. Eventually, it’ll be incinerated by the intense heat upon re-entry, like a meteor.

And, like a meteor, that hot ball of poop will light up the sky like a shooting star. But, as NASA warns, " your poop is not a shooting star ."