Life in a rut: if microbes are commonplace, where does that leave intelligent aliens?

A few years ago I wrote about how Mars' seasonal methane fluctuations suggested - although far from confirmed - that microbial life might be present just under the Martin surface. Now another world in our solar system, the Saturnian moon Enceladus, has ignited discussion along similar lines.

The Cassini probe conducted flybys of Enceladus over a decade, revealing that Saturn's sixth largest moon was venting geyser-like jets of material, including water vapour, from its southern polar region. The material being emitted from these vents also included organic compounds and methane, hinting that this distant moon's watery oceans may also contain alien methane-producing microbes. Whereas Titan and Europa were originally deemed the moons most suitable for life, Enceladus's status has now been boosted to second only to Mars, with conditions not dissimilar to those in the oceans of the early Earth.

Of course, unknown geochemical processes cannot be ruled out, but nonetheless the quality of the evidence is such as to invite further exploration of Enceladus. There have been at least seven potential mission designs proposed by various bodies, including NASA and ESA, to gain more information about the moon and its geysers. Several of these include landers, while others would fly through a plume in order to examine the vented material for biosignatures. However, to date none have received official funding confirmation. As it stands the first probe to arrive might be billionaire Yuri Milner's privately-funded Breakthrough Enceladus, rather than one from a major organisation. However, don't hold your breath: the earliest any of these missions is likely to reach Enceladus is at some point in the 2030s.

What happens if future probes find evidence of microbial life on both Mars and Enceladus? Or even, whenever a method is found to reach it, in the ice-covered oceans of Jupiter's moon Europa? The first key fact will be whether they are genetically independent of Earth biota or if the panspermia hypothesis - the delivery of microbes via cometary and meteorite impact - has been proven. If that turns out not to be the case and multiple instances of life arose separately within a single solar system, this has some profoundly mixed implications for the search for extraterrestrial intelligence (SETI). After all, if simple life can arise and be sustained on three or even four very different worlds - including bodies far outside their solar system's 'Goldilocks zone' - then shouldn't this also imply a much higher chance of complex alien life evolving on exoplanets? 

Yet despite various SETI programmes over the past few decades, we have failed to pick up any signs of extraterrestrial intelligence - or at least from other technological civilisations prepared to communicate with radio waves, either in our galactic neighbourhood or with super high-powered transmitters further away. This doesn't mean they don't exist: advanced civilisations might use laser pulses at frequencies our SETI projects currently don't have the ability to detect. But nonetheless, it is a little disheartening that we've so far drawn a blank. If there is microbial life on either Mars or Enceladus - or even more so, on both worlds, never mind Europa - then a continued lack of success for SETI suggests the chances of intelligent life evolving are far lower than the probability of life itself arising.

In effect, this means that life we can only view via a microscope - and therefore somewhat lacking in cognitive ability - may turn out to be common, but intelligence a much rarer commodity. While it might be easy to say that life on both Enceladus and Mars wouldn't stand much of a chance of gaining complexity thanks to the unpleasant environmental conditions that have no doubt existed for much of their history, it's clear that Earth's biota has evolved via a complex series of unique events. In other words, the tortuous pathways of history have influenced the evolution of life on Earth.

Whereas the discovery of so many exoplanets in the past decade might imply an optimistic result for the Drake equation, the following factors, being largely unpredictable, infrequent or unique occurrences, might suggest that the evolution of complex (and especially sapiens-level intelligent) life is highly improbable:

• The Earth orbits inside the solar system's Goldilocks zone (bear in mind that some of the planets have moved from the region of space they were created in) and so water was able to exist in liquid form after the atmospheric pressure became high enough.
• The size and composition of the planet is such that radioactivity keeps the core molten and so generates a magnetic field to block most solar and cosmic radiation.
• It is hypothesised that the Earth was hit by another body, nicknamed Theia, that both tilted the planet's axis and caused the formation of the Moon rather than having a catastrophic effect such as tearing our world apart, knocking it on its side (like Uranus) or removing its outer crust (like Mercury).
• The Moon is comparatively large and close to the Earth and as such their combined gravitational fields help to keep Earth in a very stable, only slightly eccentric orbit. This is turn has helped to maintain a relatively life-friendly environment over the aeons. 
• The Earth's axial tilt causes seasons and as such generates a simultaneous variety of climates at different latitudes, providing impetus for natural selection.
• The Great Unconformity and hypothesised near-global glaciation (AKA Snowball Earth) that might have caused it suggests this dramatic period of climate change led to the development of the earliest multi-cellular life around 580 million years ago.
• Mass extinctions caused rapid changes in global biota without destroying all life. Without the Chicxulub impactor for example, it is unlikely mammals would have radiated due to the dominance of reptiles on the land.
• Ice ages over the past few million years have caused rapid climate fluctuations that may have contributed to hominin evolution as East African forests gave way to grasslands.

The evolutionary biologist Stephen Jay Gould often discussed 'contingency', claiming that innumerable historical events had led to the evolution of Homo sapiens and therefore that if history could be re-run, most possible paths would not lead to a self-aware ape. Therefore, despite the 4,800 or so exoplanets discovered so far, some within their system's Goldilocks zone, what is the likelihood such a similar concatenation of improbable events would occur of any of them? 

Most people are understandably not interested in talking to microbes. For a start, they are unlikely to gain a meaningful reply. Yet paradoxically, the more worlds that microbial life is confirmed on, when combined with the distinct failure of our SETI research to date, the easier it is to be pessimistic; while life might be widespread in the universe, organisms large enough to view without a microscope, let alone communicate with across the vast reaches of interstellar space, may be exceedingly rare indeed. The origins of life might be a far easier occurrence than we used to think, but the evolution of technological species far less so. Having said that, we are lucky to live in this time: perhaps research projects in both fields will resolve this fundamental issue within the next half century. Now wouldn't that be amazing?

The Twelve (Scientific) Days Of Christmas

As Christmas approaches and we get over-saturated in seasonal pop songs and the occasional carol, I thought it would be appropriate to look at a science-themed variation to this venerable lyric. So without further ado, here are the twelve days of Christmas, STEM-style.

12 Phanerozoic periods

Although there is evidence that life on Earth evolved pretty much as soon as the conditions were in any way suitable, microbes had the planet to themselves for well over three billion years. Larger, complex organisms may have gained a kick-start thanks to a period of global glaciation - the controversial Snowball Earth hypothesis. Although we often hear of exoplanets being found in the Goldilocks zone, it may also take an awful lot of luck to produce a life-bearing environment. The twelve geological periods of the Phanerozoic (literally, well-displayed life) cover the past 542 million years or so and include practically every species most of us have ever heard of. Hard to believe that anyone who knows this could ever consider our species to be the purpose of creation!

11 essential elements in humans

We often hear the phrase 'carbon-based life forms', but we humans actually contain over three times the amount of oxygen than we do of carbon. In order of abundance by mass, the eleven vital elements are oxygen, carbon, hydrogen, nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine and magnesium. Iron, which you might think to be present in larger quantities, is just a trace mineral; adults have a mere 3 or 4 grams. By comparison, we have about 25 grams of magnesium. In fact, iron and the other trace elements amount to less than one percent of our total body mass. Somehow, 'oxygen-based bipeds' just doesn't have the same ring to it.

10 fingers and toes

The evolution of life via natural selection and genetic mutation consists of innumerable, one-off events. This is science as history, although comparative studies of fossils, DNA and anatomy are required instead of written texts and archaeology. It used to be thought that ten digits was canonical, tracing back to the earliest terrestrial vertebrates that evolved from lobe-finned fish. Then careful analysis of the earliest stegocephalians of the late Devonian period such as Acanthostega showed that their limbs terminated in six, seven or even eight digits. The evolution of five-digit limbs seems to have occurred only once, in the subsequent Carboniferous period, yet of course we take it - and the use of base ten counting - as the most obvious of things. Just imagine what you could play on a piano if you had sixteen fingers!

9 climate regions

From the poles to the equator, Earth can be broadly divided into the following climate areas: polar and tundra; boreal forest; temperate forest; Mediterranean; desert; dry grassland; tropical grassland; tropical rainforest. Mountains are the odd region out, appearing in areas at any latitude that contains the geophysical conditions suitable for their formation. Natural selection leads to the evolution of species suited to the local variations in daylight hours, weather and temperature but the labels can be deceptive; the Antarctic for example contains a vast polar desert. We are only just beginning to understand the complex feedback systems between each region and its biota at a time when species are becoming extinct almost faster than they can be catalogued. We upset the relative equilibrium at our peril.

8 major planets in our solar system

When I was a child, all astronomy books described nine known planets, along with dozens of moons and numerous asteroids. Today we know of almost four thousand planets in other solar systems, some of a similar size to Earth (and even some of these in the Goldilocks zone). However, since 1996 our solar system has been reduced to eight planets, with Pluto amended to the status of a dwarf planet. Technically, this is because it fails one of the three criteria of major planets, in that it sometimes crosses Neptune’s orbit rather than sweeping it clear of other bodies. However, as there is at least one Kuiper belt object, Eris, almost as large as Pluto, it makes sense to stick to a definition that won’t see the number of planets continually rise with each generation of space telescope. This downgrading appears to have upset a lot of people, so it’s probably a good to mention that science is as much a series of methodologies as it is a body of knowledge, with the latter being open to change when required - it’s certainly not set-in-stone dogma! So as astronomer Neil DeGrasse Tyson and author of the best-selling The Pluto Files: The Rise and Fall of America's Favorite Planet put it: "Just get over it!"

7 colours of the rainbow

This is one of those everyday things that most of us never think about. Frankly, I don't know anyone who has been able to distinguish indigo from violet in a rainbow and yet we owe this colour breakdown not to an artist but to one of the greatest physicists ever, Sir Isaac Newton. As well as fulfilling most of the criteria of the modern day scientist, Newton was also an alchemist, numerologist, eschatologist (one of his predictions is that the world will end in 2060) and all-round occultist. Following the mystical beliefs of the Pythagoreans, Newton linked the colours of the spectrum to the notes in Western music scale, hence indistinguishable indigo making number seven. This is a good example of how even the best of scientists are only human.

6 mass extinction events

Episode two of the remake of Carl Sagan's Cosmos television series featuring Neil DeGrasse Tyson was called 'Some of the Things That Molecules Do'. It explored the five mass extinction events that have taken place over the past 450 million years. Tyson also discusses what has come to be known as the Holocene extinction, the current, sixth period of mass dying. Although the loss of megafauna species around the world has been blamed on the arrival of Homo sapiens over the past 50,000 years, the rapid acceleration of species loss over the last ten millennia is shocking in the extreme. It is estimated that the current extinction rate is anywhere from a thousand to ten thousand times to the background rate, resulting in the loss of up to two hundred plant or animals species every day. Considering that two-thirds of our pharmaceuticals are derived or based on biological sources, we really are shooting ourselves in the foot. And that's without considering the advanced materials that we could develop from nature.

5 fundamental forces

Also known as interactions, in order from strongest to weakest these are: the strong nuclear force; electro-magnetism; the weak nuclear force; and gravity. One of the most surprising finds in late Twentieth Century cosmology was that as the universe expands, it is being pushed apart at an ever-greater speed. The culprit has been named dark energy, but that's where our knowledge ends of this possible fifth force. Although it appears to account for about 68% of the total energy of the known universe, the label 'dark' refers to the complete lack of understanding as to how it is generated. Perhaps the most radical suggestion is that Einstein's General Theory of Relativity is incorrect and that an overhaul of the mechanism behind gravity would remove the need for dark energy at all. One thing is for certain: we still have a lot to learn about the wide-scale fabric of the universe.

4 DNA bases

Despite being one of the best-selling popular science books ever, Bill Bryson's A Short History of Nearly Everything manages to include a few howlers, including listing thiamine (AKA vitamin B1) as one of the four bases, instead of thymine. In addition to an understanding how the bases (adenine, cytosine, guanine and thymine) are connected via the double helix backbone, the 1953 discovery of DNA's structure also uncovered the replication mechanism, in turn leading to the development of the powerful genetic editing tools in use today. Also, the discovery itself shows how creativity can be used in science: Watson and Crick's model-building technique proved to be a faster way of generating results than the more methodical x-ray crystallography of Rosalind Franklin and Maurice Wilkins - although it should be noted that one of Franklin's images gave her rivals a clue as to the correct structure. The discovery also shows that collaboration is often a vital component of scientific research, as opposed to the legend of the lonely genius.

3 branches of science

When most people think of science, they tend to focus on the stereotypical white-coated boffin, beavering away in a laboratory filled with complex equipment. However, there are numerous branches or disciplines, covering the purely theoretical, the application of scientific theory, and everything in between. Broadly speaking, science can be divided into the formal sciences, natural sciences and social sciences, each covering a variety of categories themselves. Formal sciences include mathematics and logic and has aspects of absolutism about it (2+2=4). The natural or 'hard' sciences are what we learn in school science classes and broadly divide into physics, chemistry and biology. These use observation and experiment to develop working theories, but maths is often a fundamental component of the disciplines. Social or 'soft' sciences speak for themselves, with sub-disciplines such as anthropology sometimes crossing over into humanities such as archaeology. So when someone tells you that all science is impossibly difficult, you know they obviously haven't considered just what constitutes science!

2 types of fundamental particles

Named after Enrico Fermi and Satyendra Nath Bose respectively, fermions and bosons are the fundamental building blocks of the universe. The former, for example quarks and electrons, are the particles of mass and obey the Pauli Exclusion Principle, meaning no two fermions can exist in the same place in the same state. The latter are the carriers of force, with photons being the best known example. One problem with these particles and their properties such as angular momentum or spin is that most analogies are only vaguely appropriate. After all, we aren't used to an object that has to rotate 720 degrees in order to get back to its original state! In addition, there are many aspects of underlying reality that are far from being understood. String theory was once mooted as the great hope for unifying all the fermions and bosons, but has yet to achieve absolute success, while the 2012 discovery of the Higgs boson is only one potential advance in the search for a Grand Unifying Theory of creation.

1 planet Earth

There is a decorative plate on my dining room wall that says "Other planets cannot be as beautiful as this one." Despite the various Earth-sized exoplanets that have been found in the Goldilocks zone of their solar system, we have little chance in the near future of finding out if they are inhabited as opposed to just inhabitable. Although the seasonal methane on Mars hints at microbial life there, any human colonisation will be a physically and psychologically demanding ordeal. The idea that we can use Mars as a lifeboat to safeguard our species - never mind our biosphere - is little more than a pipedream. Yet we continue to exploit our home world with little consideration for the detrimental effects we are having on it. As the environmental movement says: there is no Planet B. Apart from the banning of plastic bags in some supermarkets, little else appears to have been done since my 2010 post on reduce, reuse and recycle. So why not make a New Year’s resolution to help future generations? Wouldn’t that be the best present for your children and your planetary home?