Elon Musk has revealed the first picture of his company's spacesuits, to be worn by SpaceX astronauts as they venture into space and eventually to Mars.

Musk, who is chief executive of electric car company Tesla and rocket manufacturer SpaceX, posted the image to Instagram on 23 August, days after saying the suits, developed for Nasa, are currently undergoing mobility and safety tests.

The billionaire entrepreneur, who has stated he wants to colonise Mars by 2040, claims the suit is real and functional, not just a mockup.

In the Instagram post Musk said: "First picture of SpaceX spacesuit. More in days to follow. Worth noting that this actually works (not a mockup). Already tested to double vacuum pressure. Was incredibly hard to balance esthetics and function. Easy to do either separately."

Although it is difficult to tell from a single photo, but Musk's SPaceX suit appears to be more compact than those currently used by Nasa, giving astronauts more freedom to move around and observe their surroundings.

The suit's inspiration may have come from Jose Fernandez, the designer of costumes for Iron Man, Spider-Man, Batman and Captain America, who revealed in 2016 that he had been contacted by Musk to create a space suit.

First picture of SpaceX spacesuit. More in days to follow. Worth noting that this actually works (not a mockup). Already tested to double vacuum pressure. Was incredibly hard to balance esthetics and function. Easy to do either separately.

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"SpaceX reached out to me to ask if I would create a space suit. I didn't know what SpaceX was and I thought it was a film. Then I realised it's an actual space programme. They were looking to get a suit built for Elon to look at for the programme," Fernandez told Bleep Magazine.

At first Fernandez only created a helmet, but after designs submitted from elsewhere were rejected by SpaceX, the costume designer was asked to work with Musk on an entire suit.

Recalling Musk's wish to make the suit both functional and stylish, Fernandez added: "He kept saying: 'Anyone looks better in a tux, no matter what size or shape they are,' and when people put this space suit on he wants them to look better than they did without it, like a tux. You look heroic in it. It's an iconic thing to be a part of."