Shatner, one of history’s most recognizable science fiction stars, finally became a real space traveler on Blue Origin’s second crewed mission, calling it the most profound experience of his life.

“I saw a cold, dark, black emptiness. It was unlike any blackness you can see or feel on Earth. It was deep, enveloping, all-encompassing. I turned back toward the light of home. I could see the curvature of Earth, the beige of the desert, the white of the clouds and the blue of the sky. It was life. Nurturing, sustaining, life. Mother Earth. Gaia. And I was leaving her,” reads an excerpt from “Boldly Go” that was first published by Variety.

“Everything I had thought was wrong,” it reads. “Everything I had expected to see was wrong.”

While he had expected to be awed at the vision of the cosmos, seen without the filter of the Earth’s atmosphere, he instead became overwhelmed by the idea that humans are slowly destroying our home planet. He felt one of the strongest feelings of grief he’s ever encountered, Shatner wrote.

“Fifty-five or 60 years ago I read a book called “Silent Spring” by Rachel Carson. She wrote about the environmental issues that are still happening today. I’ve been a verbal ecologist since then. I’ve been aware of the changing Earth and my apprehension for all of us.

It’s like somebody owing money on a mortgage, and they don’t have the payments. And they think, “Oh, well, let’s go to dinner and not think about it.”

But it’s so omnipresent! The possibilities of an apocalypse are so real. It’s hard to convince people — and especially certain political people — that this is not on our doorstep any longer. It’s in the house.

When I got up to space, I wanted to get to the window to see what it was that was out there. I looked at the blackness of space. There were no dazzling lights. It was just palpable blackness. I believed I saw death.

And then I looked back at the Earth. Given my background and having read a lot of things about the evolution of Earth over 5 billion years and how all the beauty of nature has evolved, I thought about how we’re killing everything.

I felt this overwhelming sadness for the Earth.”