IS EARTH the only place in the universe where life exists or has existed? Perhaps not.

A few days ago, the Mars curiosity rover, a very sophisticated remote-controlled roving laboratory, drilled into some rocks and found organic molecules.

On their own, these chemicals don’t prove that there was (or perhaps may still be) life on Mars, but the evidence is mounting. As a planet, Mars has fascinated the scientific and creative among us for thousands of years.

Mars is unmistakeable in the night sky, with its shimmering reddish tinge. As the fourth rock from the sun, it’s one of our closest neighbours.

It has a thin atmosphere, too thin to support human life, but there is abundant evidence that at one time it had liquid water creating many surface features in the rocks that we see on earth; old, dried up water channels, valleys created by ancient rivers and signs of erosion.

Just like Earth it has polar ice caps.

Conditions for life on Mars were at one time favourable. All of this means it’s very plausible that Mars could have been a planet that harboured life at one time.

Mars is about half the size of earth and a Martian day lasts about 40 minutes longer than our day. Its orbit around the sun is much longer.

A Martian year lasts for nearly two earth years.

Many ancient civilisations from the Chinese to the Sumerians observed and commented on Mars. To the Sumerians Mars represented the God of War. The Chinese called it the “fire star”. Galileo was the first person to observe Mars through a telescope in 1610 and the Dutch astronomer, Christiaan Huygens, was the first person to map the surface of Mars in 1659.

Mars took on a whole new significance in 1877 when the Italian astronomer Giovanni Schiaparelli drew what he called “canali” or canals on a new map of Mars. Canals on earth are human constructions. Could Martian canals be the product of alien life forms?

Scientists were split – some believed they proved Mars was inhabited by an advanced civilisation. Astronomers, like Percival Lowell the famous American astronomer, also claimed to see the canals and much more besides – seas and areas of vegetation.

Physicist Nikolas Tesla claimed he had detected radio signals from Mars.

Others claimed that a beam of light had been detected that originated on Mars. Mars fever was at its height at the turn of the 20th Century. Sadly, the canals are not real – what Schiaparelli saw was an optical illusion.

Such was the notoriety of the “scientific” claims about Martian civilisations, it’s not surprising that stories about them contacting, invading or simply communicating with us became commonplace.

One of the earliest pieces of recorded science fiction written in the 17th and 18th Century involves stories of beings from Mars contacting the people of Earth. The most famous science fiction story based on Mars is “War of the Worlds” by HG Wells, published in 1898. In this terrifying tale Martians in huge battle-ready tripods invade earth – determined to kill and conquer us.

Wells was a science teacher who used his knowledge and understanding of life to combine fact and fiction, creating a terrifying tale. In 1938 Orson Welles, the celebrated actor and film director, generated real-life hysteria in the US when his radio play, based on Welles’s story, was broadcast as live as “breaking news”. This was “fake news” at its best and worst.

In 1976, people were very excited when a Mars orbiter took photographs of the surface that revealed a giant face carved onto surface rocks. The idea of ancient civilisations on Mars had a brief resurgence, but alas it was no more than a trick of the light.

In the mid-1980s another startling revelation once more raised the prospect of the possibility of life on Mars.

A meteorite, found in Antarctica, appeared to show evidence of fossilised bacteria. To this day the scientists still argue if these structures show traces of ancient life on Mars.

Our fascination with the red planet, along with its proximity and similarity to earth means that to date we’ve sent 45 space missions to Mars. Many failed, but four rovers that roam the surface of Mars have been successfully deployed to gather and send back information.

This includes data that shows rising and falling levels of methane – often associated with life – changing with the Martian seasons.

When we look at all the known, verifiable scientific evidence from the presence of methane, water, organic molecules to the possibility of fossilised microbes, then the probability that life once existed on Mars increases. To be honest, given the vastness of the universe, it’s very unlikely that we are alone.