EXACTLY HOW LIFE STARTED ON EARTH

In the icy wastes of space, a clue that we’re not alone

COuld there really be primitive life busily trying to evolve on an icy wasteland moon of Saturn called Enceladus? If indeed there is, we should all gaze at the sky tonight in wonder.

For what is so extraordinary about Nasa’s claims is that Saturn – in cosmic terms – is so amazingly close to us. We may not be able to see its famous rings without a telescope. But to the unaided eye, it appears as a bright and very beautiful golden ‘star’, not twinkling but shining with a steady light.

Although it is almost 800million miles away, the fact we can see the planet whose moon may be host to primitive life is almost spooky, imparting a very tangible sense that we may not be alone.

Earlier this year a team of international scientists using advanced telescopes announced they had discovered at least three planets with benign conditions which might support life orbiting a red dwarf star, equivalent to our sun. They described it as a ‘holy grail’ in the search for evidence of extraterrestrials.

But those planets were 39 light years away – or 240trillion miles. This ‘new frontier’ on Enceladus is very much closer to home.

And the fact that Nasa has now identified hydrogen on the moon means there is a possibility that primitive microscopic single-celled animals could be thriving on Saturn’s sixth largest moon.

The evidence from the Cassini probe indicates that if so, they would be living on the sides of hot jets called hydrothermal vents, sunk deep in ocean floors beneath the moon’s frozen surface.

Amazingly, this is almost a carbon copy of how life began on Earth. Or, to put it another way, it is just the type of brutal beginning that our own planet’s first creatures endured.

In March, British scientists produced powerful evidence to show the evolution of life on Earth began around similar seafloor vents to those on Enceladus. They had discovered proof of the world’s oldest fossils, which are up to 4.28billion years old, in Quebec, Canada.

These tiny fossils – half a millimetre long and half the width of a human hair – are believed to be the remains of bacteria that lived underwater around hydrothermal vents deep in

‘A soup of chemicals’

Earth’s primordial oceans. ‘The origins of life may have developed very soon after the oceans formed 4.4billion years ago,’ says Matthew dodd, a university College london geochemist who led the study.

Those bacteria are not only ancient, they are extremely resilient. ‘The microfossils’ structures are almost identical to micro-organisms we see in similar hydrothermal vents today,’ adds dodd.

This parallel with the origins of life on Earth, in particular, is why astronomers and evolutionary scientists are in such a froth of excitement and speculation.

But the speculation should be tempered with pragmatism.

Before anyone jumps to the conclusion that any primitive organisms that did exist on Enceladus could evolve into advanced life forms, we have to accept that conditions on the moon are more hostile than it is possible to believe.

The hot rocks at the bottom of Enceladus’s oceans that give rise to the thermal vents where life may exist push the liquid environment to 90C. If a fish did evolve, it would be instantly broiled and battered.

These boiling reservoirs are vaporised into high-pressure plumes of fluid that are shot in 800mph jets through cracks in the moon’s surface, where they fly hundreds of feet above. Some of them even get sucked into one of Saturn’s rings as space debris. That’s where many of the moon’s possible inhabitants are most likely to end up. Or they might land back on the icebound wasteland that is the surface of Enceladus, where temperatures are a nightmare minus 201C, and the only atmosphere detected is volcanic gas and those vapour plumes.

Which brings us back to Earth – both literally and metaphorically.

The fact is that our planet provided the perfect benign conditions to support rapid evolution.

Earth’s nurturing oceans, warm air and vast continents allowed those first micro-organisms to develop into ever more complex creatures – to crawl from the sea, to colonise the land and sky, and to evolve and keep evolving, to create the world that we enjoy today.

Those ancient fossils of life’s first creatures show that, in cosmic terms, life on Earth evolved very rapidly indeed.

Back in the 1940s, a renowned Italian physicist Enrico Fermi suggested that, with 100billion stars in our galaxy, it was logically inevitable that intelligent life should have evolved elsewhere in the universe as well.

What’s more, he added, a highly evolved extra-terrestrial life form should have colonised the galaxy by

now. Some scientists go so far as to say that there are around 60billion planets in the Milky Way alone capable of supporting life.

But that leaves a huge paradox, which has become known as the Fermi paradox – if this is true, where are the aliens? Why, despite our ever growing knowledge of space and 40 years of intensive searching, can we not find them?

The answer may simply be that conditions on Earth are unique. That only a many-billions-to-one combination of random factors has led to the conditions on Earth that support higher forms of life such as us humans.

Astronomer Royal Martin Rees says that, even if all the ingredients for life were there on any body such as Enceladus, there is no guarantee of its existence even in a primordial form.

‘We don’t know how the first life was generated from a soup of chemicals,’ he explains.

‘It might have involved a fluke so rare that it happened only once in the entire galaxy – like shuffling a whole pack of cards into perfect order.’

Which is why we should raise our eyes to Saturn tonight – and thank our lucky stars for the wonders of our blue planet.