Nasa expert says the 'bunker' is simply effect of shadows in the image

'You can see a person behind the bunker's window,' Gignac claims

Spotted 'bunker' in an image taken by the Nasa rover Opportunity

From alien coffins to fossilised lizards, conspiracy theorists believe they have found all manner of strange items in Nasa's images of Mars.

Now, one alien hunter claims to have spotted what he believes to be a bunker on the red planet, with armed people peering out of its windows.

Andre Gignac says he made the 'stunning discovery' in a photograph released by Nasa and taken by the Mars rover Opportunity.

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A conspiracy theorist claims to have spotted what he believes to be a bunker on the red planet, with armed people peering out of its windows (shown by the dotted red line)

He says he became suspicious about a 'dark spot' on the rim of the Endeavour crater he had found in the original image, and so took a closer look.

'I was stunned. It was a massive panoramic window built in the inside wall of the crater,' Gignac told Cryptozoology News.

'You can see a person behind the bunker's window,' the 58-year-old added.

He claims that the 'bunker' 'could also be a corridor leading to a bigger bunker'. 'Also, not far from this bunker are missiles, rockets and structures deployed in a circle,' he says.

'Bunkers have been spotted in previous Nasa pictures, some might be caused by shadows or lack of resolution that doesn't give enough detail to clearly see if the structure is a bunker or not,' Nigel Watson, author of the UFO investigations Manual, told Dailymail.com

Andre Gignac says he made the 'stunning discovery' in a photograph released by Nasa and taken by the Mars rover Opportunity

Pictured From left to right, are structures, missiles and rockets Cignac claims he found in Nasa's image

Cignac claims he became curious about a 'dark spot' on the rim of the Endeavour crater he had found in the original image, and so took a closer look

'Others have claimed that bunker pictures were taken by the European Space Agency, Mars Express orbital vehicle.

'These were explained as being of erosional features or caused by the way the pictures were stitched together.

'Whatever the "mundane" explanation I think we are more fascinated by the idea that there are people secretly living beneath the surface of Mars and they are part of some secret space program.

'Such a project would need vast resources and would be very hard to keep covered up, yet many think this is what is happening and that these activities are being carried out in conjunction with one or more alien species.'

The latest discovery follows a spate of supposed 'sightings' of Martian civilisation.

Last year, a Maryland-based UFO hunter spotted what he believed to be a 'decorative' box on the red planet.

Other objects found in images of Mars include what some UFO hunters claim to be a fossilised iguana (left). Stock image of an iguana is pictured right

The so-called 'coffin' was found by Will Farrar from WhatsUpintheSky37 as he trawled through a library of pictures sent back by the Mars rover Curiosity. The image pictured inset has been edited

The 'coffin' was discovered by Will Farrar from WhatsUpintheSky37 as he trawled through a library of pictures sent back by the Mars rover Curiosity.

IS THIS A CASE OF PAREIDOLIA? Many scientists believe that seeing strange objects, such as a 'coffin' on Mars, is simple a case of pareidolia. This is a psychological response to seeing faces and other significant and everyday items in random places. It is a form of apophenia, which is when people see patterns or connections in unconnected data. There have been multiple occasions when people have claimed to see religious images and themes in unexpected places, especially the faces of religious figures. Many involve images of Jesus, the Virgin Mary and the word Allah. For example, in September 2007 a callus on a tree resembled a monkey, leading believers in Singapore to pay homage to the Monkey god. Another famous instance was when Mary's face was a grilled cheese sandwich. Images of Jesus have even been spotted inside the lid of a jar of Marmite and in a potato. Advertisement

'This little box sure does look like a modern coffin concrete liner,' he wrote on his YouTube channel.

'As well as the stonework on the back part of the hill that looks like stairs or some left over stonework from some old civilisations constructions.'

Alien researcher Scott Waring of the UFO Sightings Daily said he believes the coffin was made from a stone-like substance.

'What would it take to get Nasa to turn the rover around and examine the contents of this box?,' he said.

But while its strong lines have captured the imagination of UFO bloggers, scientists believe sightings such as this are down to a psychological phenomenon called Pareidolia.

This describes the brain's response to seeing faces and other significant objects in random places.

It has evolved so that human eyes can spot faces within their environment, and to help them recognise friends in a crowd.

Scientists claim we also tend to use this ability to 'enrich our imagination' and recognise meaningful shapes, even when they're not there.

'I stand ready to be convinced that I have possibly hallucinated. I won't mind being told that I'm wrong,' Cignac says.