Idea of life on Mars is no longer really out of this world
Final frontiers are in meagre supply nowadays. People tweet from the summit of Mount Everest, take pleasure cruises of the Arctic Circle, book luxury tours through the Gobi Desert.
For those with the cash and the inclination, few places in the world are truly off limits. In fact, 'dark tourism' specialists even offer whistle-stop visits to such safety-not-guaranteed locales as Afghanistan's Hindu Kush mountains and militarised Kashmir.
Maybe that is why Mars, in the news this week for a multitude of reasons, continues to exert a tug on humanity's consciousness.
Hovering just on the edges of our imagination, the Red Planet is the closest thing to a 'Here Be Dragons' point on the map in 2015. Hence the worldwide excitement as Nasa confirmed water ('ephemeral brine' in astrophysicist lingo) had been detected on the surface.
When H20 was found on moons orbiting Jupiter and Saturn, everybody shrugged. Mars is different. It feels within reach, a place we can picture hitching a lift to one day.
Piggy-backing on the hype is 'The Martian', a new Ridley Scott romp chronicling the travails of an astronaut (brave Matt Damon) stranded on the Red Planet who must utilise real-world science (or the sexy Hollywood approximation thereof) to jerry-rig his way home.
As with Nasa and its ephemeral brine, having Mars as backdrop has undoubtedly elevated the film's appeal. Would a movie named The Venetian have enjoyed anything like the same prominence?
Mars has an almost mythological allure, analogous to the spell cast by the American West in the early years of cinema. It's 30 million miles away and no human has ever set foot there, and yet it feels peculiarly familiar - no more 'alien' than the North Pole or the Amazon Basin. If humankind had a bucket list of places to visit, Mars would be right up there.
From the 19th Century onwards, Mars has loomed in the collective imagination. When, in 'The War of the Worlds', HG Wells conceived of a race of extraterrestrials laying waste to Mother England in clanking tripods, he naturally determined that they should come from the fourth rock from the sun.
Alien invaders of the B movie era inevitably originated from the Red Planet too. We perceived Mars as an opportunity, but also a threat, a place that could elevate humanity if we could reach it, but with the potential to destroy us too.
No such complex feelings attended our relationship with Venus, Jupiter etc. They simply hang in the void, lifeless conglomerations of rock and gas. There's a reason David Bowie never penned a song called 'Life on Saturn'.
Arguably, our fascination with Mars is rooted in a deep-seated survival extinct. The sun is known to be halfway through its natural life span and in a little over a billion years will begin to swell, scorching the Earth with killer rays. A relative hopscotch away amid the vastness of space, Mars represents a logical life capsule for homo sapiens.
Escaping our broiling home world by relocating en masse to Mars would buy enough time to plan the conquest of distant galaxies.
It this sounds like science fiction, or even science fantasy, consider that billionaire entrepreneur Elon Musk (creator of the Tesla electric car) has asserted that Martian colonisation is crucial for the survival of the species.
He even advocates 'terraforming' the planet by nuking its poles, thus triggering accelerated climate change that would create a breathable atmosphere.
"Sooner or later, we must expand life beyond this green and blue ball - or go extinct," he has said.
Stephen Hawking agrees. Eventually, the world's most famous scientist contends, we're going to have to quit the Earth - and Mars is a logical stepping stone.
"It is essential that we colonise space," he has stated. "I believe that we will eventually establish self-sustaining colonies on Mars and other bodies in the solar system."
Perhaps that's why Mars grips us so. We see it twinkling in the night sky and sense, at some primordial level, that it is where our future lies.