Onscreen in the sci-fi odyssey “Annihilation,” an expedition ventures deep into a foreboding terrain known only as Area X, carrying guns and harboring mounting suspicions about one another.

These soldiers — a psychologist (Jennifer Jason Leigh), a biologist (Natalie Portman), a paramedic (Gina Rodriguez), a physicist (Tessa Thompson) and an anthropologist (Tuva Novotny) — enter what is about to become a living, breathing nightmare, an environmental disaster zone without scientific explanation, as filtered through the mind of “Ex Machina” director Alex Garland, adapting the first book in Jeff VanderMeer’s “Southern Reach” trilogy.

That they’re all complex and dimensional female characters is at once trailblazing and, refreshingly, perfectly normalized.

“Each of the women have their own destructive behavior,” said Portman, who brings steely intensity to the role of Lena, the biologist with her own reasons for volunteering for the dangerous mission, in Friday’s release. “I find that so beautiful. That’s the greatest science fiction, when the psychological becomes externalized.

“And to have five women at the center of this expedition — we’re so used to seeing five men going and doing something together, it’s not even questioned why it’s always all men. To give that same kind of attitude to five women is really unique.”

The sisterhood struck on the London set of “Annihilation” is strong among Portman, Rodriguez and Thompson, reunited in a suite at the Hollywood Roosevelt Hotel ahead of the film’s Los Angeles world premiere.

Sitting side by side on a couch with their legs curled up, the camaraderie came flooding back in waves of laughter and mutual admiration.

“I feel like (‘Annihilation’) is the kind of movie where, if you’ve seen it only once, you haven’t seen it,” said Thompson. “One of Alex’s references for this film was (Andrei Tarkovsky’s) ‘Stalker,’ which I watched a couple times in anticipation of making this movie, trying to figure out what that film is and means. It felt like being inside of a meditation.”

“Ooooh!” gasped Rodriguez. “That’s poetic. It’s like being inside of a meditation.”

“But you know what I mean? It’s a very meditative, lyrical film, and we don’t have a lot of practice as audience members with that kind of content, particularly in American film,” Thompson continued.

“I feel like we reject it quickly, too, the way they did with Darren Aronofsky’s ‘mother!,’ which I loved,” added Rodriguez, gesticulating to the sky. “I thought it was Jennifer (Lawrence)’s best performance. It made me think for hours. Art that moves you in any which way, whether it’s positively or negatively — it’s working.”

Part philosophical sci-fi, part psychedelic-existential fever dream, “Annihilation” pulses with the looming unease of the unknown. That unknown lurks in the darkness of the vast swamplands and marshes of the Southern Reach, marked by the beauty and horrors of nature run amok, and perhaps more disturbingly in the disquiet of confronting those same mysteries within oneself.

Self-destruction is in our DNA, the film posits. Its approach, however, is one of empathy. And the journeys the three stars went on in search of their characters, expanded in collaboration with Garland from the sparsely detailed counterparts in VanderMeer’s book, had profound and lasting effects.

Portman, who moved her family near the Pinewood Studios production during filming, responded to the melancholic interrogation Lena embarks on as she pushes farther into Area X while reflecting on a broken marriage (Oscar Isaac, reuniting with “Ex Machina” helmer Garland, plays her husband).

“Alex brought the (idea of) self-destructive behavior and defining the destruction of a marriage as part of that,” she said. “You could call it moralistic, but I found it very moving — that it is destructive, hurting someone that you love very deeply.”

The physicality of the shoot demanded Portman know her way around a military-issue machine gun and train with visionary dancer Bobbi Jene, whom Garland hired on Isaac’s recommendation to choreograph a memorable third-act sequence of movement.

“She would give me directions like, ‘Feel like you’re like an octopus stuck to the wall,’” raved Portman. “I wish someone was always giving me that kind of physical imagery. It was really cool.”

Thompson found a deep connection to her character Josie’s growing link with the mutations the group encounters as they get closer to the inexplicable veil of energy known as “The Shimmer.”

“There was something in it that I was really struck by in the destruction of the Earth, of how we treat the other things that are not human — the planet,” she said. “At a certain point with the destruction that we do, we will not have the technology to undo it or to even understand it.”

Rodriguez’s character, Anya, a paramedic with a physical swagger, has an outgoing personality that masks her own addictive personality and deep-seated fears — a theme that resonates in Rodriguez’s own life.

“I didn’t realize how much of my personal draw to the character was her reason for going into the Shimmer,” she admitted. “Her reason for going on a suicide mission was running away from her past and her addictive personality, her addictions, and her fear of mental illness, and her fear of losing control of herself.

“I’m always battling the idea of mental health. My fear of it personally, the history of mental health in my family, and not ever really facing it because in my culture we don’t really talk about mental health. I got to actually enter my own fear as an actor.”

Also tantalizing for Rodriguez was the chance to step outside her popular “Jane the Virgin” TV alter ego. “Being able to play this very outwardly unafraid badass … was so dope,” she said. “As an artist, you want to transform, you want to be anything, you want to be able to be capable of doing anything, and I felt like Alex was telling me I could.”

There was one caveat: She had to shave her head for the role just three days after wrapping on “Jane the Virgin.” “It was very fun to do and also really awful and scary,” she said with a laugh. “It felt like night and day. They cut all my hair off and I was like, ‘Who am I?’ And then Alex was like, ‘Let’s go on a journey of wondering who we are!’ Oh, man, it was crazy.”

If you go

ANNIHILATION

R, 120 minutes

Playing at Waterford, Westbrook, Lisbon