In 'The Space Between Us,' Asa Butterfield plays Gardner – a boyfrom Mars who travels to Earth to visit outsider teen Tulsa, played by Britt Robertson.

So far, so romantic. The only problem? His Mars-born body can’t survive in Earth’s atmosphere, and must make a choice between being with Tulsa, or sacrificing his health.

Think 'The Fault In Our Stars 'x 'The Martian 'and you’ve got it!

And aside from making us teary, the romance also means steamy make out scenes. So, when Asa Butterfield stopped by MTV to chat the new YA blockbuster, we had to know what it’s like to film those smooch scenes with his co-star.

HIT PLAY on the video below to see Asa reveal all the behind the scenes secrets… and the totally gross prank he pulled on Britt!

'- The Space Between Us is in cinemas now.'

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