When directors search for the face of innocence, they often look no further than Asa Butterfield.

“Maybe it’s my eyes,” the 19-year-old British actor speculated. “That’s what I’ve been told. I’ve always played younger. A lot of my characters have had a kind of innocence.”

Teenagers know Butterfield from his title role in the sci-fi film Ender’s Game (2013). Adults may have seen him as the youngster who lives in the roof of a Paris train station in Martin Scorsese’s period drama Hugo (2011).

Independent filmgoers will remember him from The Boy in the Striped Pajamas (2008), a World War II story in which he played the 8-year-old son of a German concentration-camp commandant. When he befriends a boy inside the camp, there are disastrous consequences.

In The Space Between Us, opening nationwide this week, Butterfield plays Gardner Elliot, the first human born on Mars. When curiosity propels him to visit Earth — a journey that’s dangerous for his unprepared body — the 16-year-old has exciting as well as life-threatening experiences.

Gary Oldman co-stars as a scientist, Carla Gugino as Gardner’s mother figure and Britt Robertson as a street-smart online friend in Colorado.

Gardner is a born adventurer — more so than the actor who plays him, Butterfield said.

“In my real life I don’t ride a motorbike or beat up bullies or steal cars,” he said, speaking by telephone from his London apartment.

Instead, Butterfield continued, he prefers to hang out with friends, cycle over to see his parents or “get some good food.” He moved to his own place in April, and reported that he’s enjoying the independence of living on his own.

Butterfield first read the script for The Space Between Us more than five years ago.

“As the different drafts were adapted,” he recalled, “Gardner got older and I got older. I grew up.

“I liked the idea of playing someone who had never set foot on Earth before,” he continued. “I had a lot of freedom and creative ideas. The director (Peter Chelsom) and I came up with this character who was sweet and innocent, but also very driven and courageous. Growing up on Mars, he has an isolated and distorted perception of everything.”

Beyond the character, the physical aspects of the role were complex. According to producer Richard Barton Lewis, who had many conversations with NASA while developing the project, Earth’s gravity is two-thirds greater than Mars’, because our planet is much bigger.

“He weighs half as much as he’d weigh on Earth,” Butterfield said, “so I had to track that development and figure out how it affects his body and the way he walks.”

In the end, though, the film was about Gardner’s inner life, not the special effects.

“The core of the character is his wonder at everything he sees,” Butterfield said, “the unbiased view he has. He’s not judgmental. He is a pure, uncorrupted soul. This is a boy who never experienced a real life, a real existence. He’s trying to find out who he is and where he came from and what his purpose is.”

Butterfield himself is well along in that process, although he is a little hazy on why he decided on acting.

“All of my family are very creative and always promoting creativity,” he said, “but none are actors.”

His father is an advertising copywriter, his mother a psychologist.

“My brother went to acting class before I did,” Butterfield continued. “My mum wanted me to go and meet new people, make some friends, because I was quite shy. I don’t think I enjoyed it for quite a while.”

Everything changed when a casting director visited the class.

“She wanted me to audition for The Boy in the Striped Pajamas,” Butterfield recalled. “I think it was just my look. The character was an innocent child.”

The drama won numerous awards, and the 10-year-old Butterfield was singled out for praise. He went on to play Mordred in the British series Merlin (2008-2009) and one of the children of Maggie Gyllenhaal’s character in Nanny McPhee Returns (2010). He also co-starred in The Wolfman (2010), A Brilliant Young Mind (2014), and 10,000 Saints (2015). Most recently he appeared in Tim Burton’s Miss Peregrine’s Home for Peculiar Children (2016).

“Growing up, I didn’t want to be an actor,” Butterfield said. “Even after those first films, I didn’t think I’d carry on doing it. I never dreamed it would go the way it did. I imagined myself digging up dinosaurs or making wildlife documentaries.

“I was 13 when I started filming Hugo, and I started to take it seriously, to understand the amount of thought that goes into it,” he recalled. “When you’re young, you don’t really act. You just go along with it and use your imagination.”

Hugo was his wakeup call.

“I wasn’t intimidated by Scorsese until we began shooting,” he said. “That’s when people started saying to me, ‘What! You’re starring in a Scorsese movie?’ I didn’t appreciate how significant that was.”

Butterfield enjoys the process of acting, but has no plans to abandon England for Hollywood.

“Being an actor in London allows you to separate your craft from the rest of your life,” he said. “In places like Los Angeles, it’s easy to get caught up in the whole machine. I want to stay grounded.

“I enjoy acting,” Butterfield continued, “but I want to do other things as well. Acting doesn’t have to be a full-time job. You can try out anything and learn a lot.”

That learning will take the place of college for Butterfield, at least for now.

“A lot of my friends are at uni,” he said, “but I was so done with education by the time I’d graduated (secondary school). I thought, ‘I’m going to chill out and control my routine and schedule for a few years before I venture back.’ ”

Butterfield recently completed shooting a film version of R.C. Sherriff’s classic 1928 play, Journey’s End, in which he co-stars with Paul Bettany, Sam Claflin, and Tom Sturridge. Set in a trench in France during a four-day period in World War I, the drama is about the experiences of a group of British officers.

“We had a chat with some soldiers who suffered from (post-traumatic stress disorder),” Butterfield said, “how it affected them and their experiences of being a soldier on the line. It was incredible and heartbreaking. One had fought in Iraq and Afghanistan, and another had fought in the Falklands War as well as Bosnia.

“I play one of the young officers,” he added. “He’s incredibly keen and optimistic and wants to serve his country.”

Butterfield recently completed a coming-of-age film, The House of Tomorrow, with Maude Apatow, Ellen Burstyn, Nick Offerman, and Alex Wolff. It’s based on Peter Bognanni’s 2011 novel.

He plays a teenager who lives in a geodesic dome with his grandmother (Burstyn), who is teaching him all about architect/​inventor R. Buckminster Fuller. When circumstances force him to leave his sheltered life, he confronts the problems facing every teenager and turns into a punk rocker.

It’s an offbeat film, but so far most of Butterfield’s career has been made up of offbeat choices, and he’s fine with that.

“The most important thing is not to take your job too seriously,” he said. “You should play around and accept your mistakes.”

The best piece of advice he’s gotten, the young actor said, came from Oscar winner Emma Thompson, who played the title role in Nanny McPhee Returns.

“She told me, ‘You should never stand up if you can be sitting down. You should never be sitting down if you can lie down,'” Butterfield recalled. “Basically she was telling me to look after myself. I think what she meant was, ‘Stay healthy and be fit, so you’ll be able to do the best you can. Take every opportunity to give yourself a break.’

“That’s always my excuse when I’m not doing anything.”

First Published January 29, 2017, 5:00 a.m.