Dark narrow streaks called recurring slope lineae emanate out of the walls of Garni crater on Mars. The dark streaks here are up to few hundred meters in length. They are hypothesised to be formed by flow of briny liquid water on Mars.

What fantastic news it was that there is almost certainly seasonal running water on Mars. While there is a remote possibility of marine life under the ice cap that envelops Europa, one of Jupiter’s larger moons, it is Mars, our so-called sister planet, which is the celestial body in our solar system which has always fascinated us.

In Victorian times we were naive enough to believe in, shall I say, manmade canals on its surface. Just as well there were no men there; had they been anything like us, they might have fancied our planet rather than their own. With Martian surface temperatures rising to never more than freezing and plummeting as low as -139°C – against our lowest of -60°C – the temptation to take over our lovely, benign habitat, would have been great.

But, seriously, it is of huge significance that there seems to be flowing water on Mars. The reason it doesn’t freeze is because of its very high salt content, mixed with sodium and magnesium perchlorate. It is thirteen times saltier than Earth’s seas and flows freely during the Martian summer. It is enough to burn your skin; not too welcoming for a dip and certainly not the sort to get a mouthful of.

The greatest question that has exercised modern humans is whether we are alone in the universe. Just to complicate matters further, it is now thought that there may, actually, be many universes. So how rare is life? We know there must be a whole set of circumstances in place to give it even a chance. Venus – a misnamed planet if ever there was one – has a surface temperature hot enough to melt lead and an incredibly dense and sulphuric atmosphere. It suffers from a runaway greenhouse effect. No chance of life there.

We know we are alone in our solar system – at least in the form of ourselves and the other life that surrounds us on Earth – but we also know that, clever as we are, we started as the lowest form of microbial life in the primordial ‘soup’ that once passed for oceans.

No one knows how that first single cell arrived or developed. Maybe it came to us riding on or in an asteroid, or comet. Or, perhaps, a chunk of another planet ricocheting off that heavenly body by an asteroid strike of its own and sent earthwards. And no one knows how that single cell divided into two and began its long journey to us. Perhaps it was a lightning strike into that primordial ‘soup’ that triggered it.

If we can establish that even microbial life once existed on a long ago, much warmer Mars, and is still there, dead or alive, then the probability is that we have companion peoples spread across the infinite reaches of the cosmos. Actually, I personally – for what it’s worth – have never doubted it. Notwithstanding how many the factors must come together to make advanced life possible, the sheer scale of the universe – and never mind the possibility of multiple universes – means that even if the odds were 10,000,000,000,000:1, it will have happened. And many times.

Our first microbial organisms began their evolutionary journey into us around 3 billion years ago. And there must be many habitable planets much older than our own which may have begun their journey into advanced life much earlier than ours. After all, the Big Bang took place nearly 14 billion years ago.  If these civilisations managed to survive into maturity, they must be hugely more advanced than us. Imagine where a thousand years will take us from where we are now – and that is just a blink in space time. Then imagine a civilisation a million years ahead.

“So, where are they?” you ask. “Why haven’t we heard from them?” The answer may be that we have, but don’t know it. Or that such smart creature – dare we say considerate – hold to Star Trek’s Prime Directive of non-interference.

Then again, it may be that the sheer immensity of the distances which separate us confound even the most advanced civilisations. “Ah, but,” I hear you say, “what about warp speed and worm holes?” Yes, but they may only be part of our wild and ever-hopeful imaginings. The simple truth could be that even the cleverest of aliens cannot overturn the iron laws of physics. Perhaps one or more of those laws block our pathways to each other for ever.

What is undoubtedly true is that sooner or later SETI (Search for Extra Terrestrial Intelligence) will hear from them in a form of encryption that we can understand. But we can never have conversations. Even at light speed, it would take far, far too long for a message to get back to the sender.

I well remember the incredible excitement which surrounded the Apollo missions and, in particular, those steps down the Luna module to make contact for the first time with the surface of an alien world. That was 1969. If only we had kept up that momentum, we would have been on Mars long ago. Instead, we chose to spend our precious resources on foreign wars, defense establishments and ever more fiendish ways of killing each other.

Having said that, I have to acknowledge that it was the Cold War and America’s refusal to be beaten to the moon that pulled off that stunning feat. NASA has shown that the final building block to possible life on Mars is there and that a permanent presence on that planet is possible. China’s interest in the Red Planet may be all that is needs to kick start a fresh race into space. I hope so. I would love to live long enough to relive a similar thrill to that which I enjoyed all those long years ago.