Forget the dress - what colour is MARS?

This time the debate involves Mars – the so-called 'red planet' – which conspiracy theorists believe is in fact more blue and green.

They argue the space agency has manipulated the colour of images from Mars to appear red, orange and pink, in what they claim is an attempt to mask life on the planet.

The debate has raged since the 1970s when Nasa's Viking 1 lander became the first spacecraft to touch down on the red planet, according to a report by Alan Boyle in NBC News.

Its initial images revealed what appeared to be a blue sky, similar to that seen on Earth, raising hopes that there may be Martian life.

Viking team member Carl Sagan announced at a press conference soon after: 'Despite the impression on these images, the sky is not blue...The sky is in fact pink.'

The sky on Earth is blue because of a phenomenon known as 'Rayleigh scattering', in which blue particles of light are scattered around by the atmosphere.

On Mars, the reverse effect takes place. The dust in the atmosphere scatters the red particles of light, makes the sky also appear red.

Nasa claims the sky appeared blue in the first Martian images because Viking's filtered photographs still had to be calibrated with the right colour balance.

But not everyone is convinced. A report by Ron Levin, a researcher at Lockheed Martin stated in a report: 'An excess of red is found on all of the Martian blue and green panels.

'Such extreme illuminations are shown to be incompatible with the grey panels.

'It appears that the true raw image data have been modified prior to publication to convert the blue and green pixels to grey, rendering a grossly changed image.'

Conspiracy theorists have made wilder claims, with one writing: 'The images were falsely reddened to make it appear there was no life, no green algae or lichen on the plane.'

Today both the Opportunity and Curiosity rover have patches of colour attached to their instruments that are used in to adjust the reflected colour to a true likeness.

(dailymail.co.uk)