They're far removed from conspiracy theorists and the everyday UFO hunter, but even veteran astronauts can get taken aback by alien-like shapes and shadows.

It turns out, no one is exempt from looking for signs that humans aren't alone in the universe.

Astronaut Shares Experience On The Shuttle

Leland Melvin, a NASA astronaut, was asked about his thoughts on alien life by UFO Sightings Daily on Twitter. In a candid moment, he answered and shared a close encounter with what appeared to be a UFO just drifting outside of the Space Shuttle.

According to Melvin, he quickly told the NASA control center about what he was seeing, but his superiors assured him that it was just ice.

BGR points out that while the explanation seems far-fetched, it actually makes sense, since a chunk of translucent ice breaking off and floating through space would appear extremely strange to an astronaut looking out from inside the shuttle.

Not everyone is convinced of the reasoning, though.

When UFO Sightings Daily followed up to ask whether the astronaut thought it's possible that ground control simply lied to him to keep him calm and focused on the shuttle, Melvin didn't write it off completely.

"Hmmm. Don't think so, but you never know," Melvin responds.

Are There Aliens Out There?

Alien life is a hotly contested subject, even in the scientific community. A recently released study even tackles the issue, saying the reason humanity hasn't encountered extraterrestrial life is because they simply aren't out there.

Of course, plenty of scientists and non-scientists remain hopeful of eventually getting proof of the existence of aliens.

All around the world, there are a lot of UFO sighting claims that happen regularly. In an effort to organize the wave of supposed sightings, scientists have revived a scale designed to classify alien encounters.

In a paper published in July 2018, the SETI Institute revised what's known as the Rio Scale and tweaked it for the modern landscape. The Rio Scale is a tool to measure the significance and credibility of each UFO event.