Melvin fielded a question last week from Scott Waring, founder of the popular blog UFO Sightings Daily. Waring asked for Melvin's "outlook about the existence of intelligent alien life living in our solar system" and whether the retired astronaut had ever witnessed a UFO.
Melvin, who's logged more than 565 hours in space, answered by saying he hasn't seen a UFO in space or on the ground. And then things got interesting when he added, "but thought I saw something organic/alien like floating out of the payload bay."
He wrote that he and NASA astronaut Randy Bresnik called down to the ground to ask what it was. NASA told them it was ice that had broken off a Freon hose. Melvin described it as "translucent, curved, organic looking" and then added an alien-head emoji at the end of the tweet.
Waring responded back with a "Wow!" and asked if NASA might have lied about what the object really was. Melvin responded with, "Hmmm. Don't think so but you never know."
If we're looking for an explanation for a bizarre sighting in space, ice sounds like a perfectly reasonable one. Melvin's last space mission took place when the shuttle Atlantis visited the International Space Station in 2009, and it appears Earth hasn't been invaded by organic/alien-like creatures since then.
CNET has reached out to Melvin to find out which mission he was on when he saw the object and what he thought it might be.