He has boldly gone where few people have gone before, and William Shatner likely will not go back.
After earning a once-in-a-lifetime ticket on Jeff Bezos' Blue Origin spacecraft in 2021, Shatner returned to Earth consumed with feelings of "grief."
He compared going back on a galactic journey to "revisiting a love affair" and told Fox News Digital in an exclusive interview that he should probably "let it alone."
Shatner's deep connection to space exploration began more than 50 years ago when he starred as Captain James T. Kirk on the legendary television series, "Star Trek."
Actor William Shatner speaks during the 15th annual official Star Trek convention at the Rio Hotel & Casino on August 6, 2016 in Las Vegas, Nevada. (Photo by Gabe Ginsberg/Getty Images)
His celestial affinity may be written in the stars now that he has plans to stay grounded for the foreseeable future, but Shatner will not stay away from interplanetary drama for too long as the host of the new FOX unscripted series, "Stars on Mars."
In 2021, Shatner made history when he became the oldest living person to travel into space during an 11-minute trek aboard the New Shepard spacecraft. He was 90 years old.
"What I experienced was not so much the flight into space, but my observation," he recalled. "Everybody knows we live on a small rock and that up to 12,500 feet oxygen is there. And after that, as you go higher, you get into a dead zone. So there's the Karman line is 50 miles up. Oxygen is two miles up. We live on a small rock. I saw the beginning of the curvature of the Earth."
"If I followed through, I could make a circle of this rock we live on. We are so negligible. We are so nothing. We are this small rock and this negligible solar system which is beside a mediocre star in a galaxy that is barely larger."
He added, "We're nothing. We are nothing, and that's what I saw. And what else I saw was the tragedy of the extinction of life."
The "T.J. Hooker" star was overcome with emotion upon landing. He explained that his tearful response to safely making it back to land was purely out of "grief" for the planet.
"The subject of ecology has interested me all my life," he said. "I know a little bit more about it than most people, and I'm in deep grief for what's happening to the Earth, and it was exacerbated by being up in space."
He was even less optimistic about the idea of humans colonizing Mars. With six-month minimum travel time to the planet and another six months circling back down to Earth, Shatner could not imagine how a crew could survive difficult conditions.
"You don't know what's flying around up there, and any one of those things would penetrate and be your destruction," he said. "I don't know how it's possible."
He also never had an inkling about the lasting impression "Star Trek" would have on the world or how his career would remain at flight forever.
When asked for insights on his secrets to his success, Shatner said, "Well you know, I jocularly answered talent but really, it's luck. It's the luck of being healthy. I think that's the first thing."
He added, "I've never, you know, I've had things happen, but nothing debilitating over a period of time. So having the life force within me is probably mostly what it's all about."
Shatner's gearing up for another leading role as the host, or Mission Control, of FOX's celebrity competition show, "Stars on Mars."
The out-of-this-world reality series launches 12 fearless celebrities to the red planet as crew members competing to conquer "Mars" until one space invader is crowned the "brightest star in the galaxy."
"Vanderpump Rules" star Tom Schwartz, former professional cyclist Lance Armstrong, UFC champion Ronda Rousey, NFL player Richad Sherman, "Real Housewives of Atlanta" star Porsha Williams Guobadia and former Super Bowl champion Marshawn Lynch will compete to win the coveted astronaut suit.
Former "Modern Family" actress Ariel Winter, comedian Natasha Leggero, "Superbad" actor Christopher Mintz-Plasse, Olympic figure skater Adam Rippon, singer Tinashe and Bruce Willis' daughter Tallulah Willis are also vying for the top prize.
While he admitted the celebrities would not be able to survive in space, Shatner was impressed with the group's determination to try something new.
"You can expect great entertainment. It's really fun," he said. "It's lighthearted. It's personable. People you will recognize are on it. They got eliminated for one reason or another, and a great bond forms between all the people."
He added, "There's sincere emotion as people leave. There's a sincerity about them going, and there is a generosity of spirit that nobody would have thought of towards the end."
Speaking of generosity, Shatner could not help but offer up condolences toward his former co-star, George Takei, in their long-running feud against each other.
Along with Nichelle Nichols and Leonard Nimoy, Takei and Shatner starred on the original TV series from 1966-69. They also both appeared in several franchise films.
Takei, who played Sulu on "Star Trek," and Shatner have been publicly battling back and forth for decades. George recently claimed he experienced "zero gravity" longer than Shatner.
"Poor George is eaten up with jealousy for 60 years," Shatner said. "I feel sorry for him."
'Stars on Mars' premieres June 5 on FOX.