Referred to as intra-terrestrial life, this biomass is particularly interesting to a number of researchers because it can shed light on how to find living things on Mars or Europa where any aliens would most likely thrive deep under the surface, in warmer environments close to geological hotspots. This is why the JOIDES Resolution, a scientific drill ship, will spend a year sailing across the Pacific and to the mid-Atlantic ridge, on a search for new microbes and tracking how they move through mazes of sub-oceanic aquifers by staining local colonies with dyes along the way. And there’s another notable point of interest for biologists here. On the one hand, life on our world could’ve started in remote, subterranean chambers and eventually moved upwards, closer to the shallow seas, hot springs, and other habitats, evolving photosynthesis while it migrated. Conversely, we can also propose that life began in the shallow seas and eventually finding its way down as new bacterial strains evolved to use the nutrients in volcanic vents, soils, and rocks to fuel its metabolism.

Studying microorganisms which may be ancestors of the hypothesized universal common ancestors in many evolutionary charts could give important clues to the validity of this theory and help us narrow down where life began. If half of all living things really make their home under oceans, continents and mountains, we need to find out why this is the case and apply what we can learn to the question of abiogenesis. After all, if we’re able to come up with a theoretically sound, evidence-backed model of how living things get their start in he kind of environments one would expect to find a newly formed planet, we’d be better equipped to either look for aliens on other promising worlds in our solar system, or construct models of how life may emerge in a very different set of conditions we could find on icy planets, moons and in other solar systems…

[ illustration by Hau Si Yuan Julian ]

Maybe the media outlet had a massive surge of traffic after it ran its first story about the search for otherworldly life, maybe the number of comments on its subsequent stories in the same vein went off the charts, or maybe it’s just a slow news day, but quite a few of the biggest newspapers and blogs around the world just keep on repackaging the same ten articles about the day we may find an alien world scurrying with living things. Don’t get me wrong, there are some very important studies that certainly deserve extensive coverage in the world of popular science, like the finding that water in meteorites can affect the chirality of amino acids, or that after exposure to typical cosmic radiation, certain chemicals in space debris become nucleobases in RNA, and a few curious ideas about finding traces of forests and vast biospheres just by looking at the light they reflect. However, articles like the Telegraph’s newsflash recounting that meteorites might have helped spark life on Earth simply fail to add anything even remotely new to an extremely popular and oft repeated theory.

I know, exciting research regarding potential aliens doesn’t happen every day. Trying to find something which may be radically different from life as we know it in almost every imaginable way without knowing what it is we’re actually trying to track down is very difficult. Even if we were to stick to searching for clear markers of life we could readily identify, these efforts require a major investment in an entire fleet of orbital telescopes and years of searching to find another terrestrial planet we could photograph with a high enough resolution to get some concrete data, something that’s simply not going to happen overnight or any time soon for that matter. Profound science like this takes time, effort and a commitment to press onward with space exploration efforts for decades to come, something sorely lacking in today’s political climate. Maybe the very real potential for the developed world to throttle back its scientific and technical leadership thanks to today’s short sighted politicians could be the pop sci subject of choice on a slow news day since this problem hasn’t been getting through to the public nearly as well as another rehash of basic astrobiology primers…

[ illustration by Frieso J. Hoevelkamp ]

However, just because Europa is still in its icy shell doesn’t mean that it can’t host life. In fact, a study looking at the tidal kneading the moon experiences, points to a warm ocean underneath all those glaciers and even a bit of energetic stirring under the surface, all promising indications for potential alien faunas. Oceanographer Robert Tyler ran a few simulations to account not just for the tidal forces acting on Europa as it orbits Jupiter and gravitationally interacts with the other large moons, but also its tilt. The idea is that the tidal kneading of a moon tilted on its axis will send a slow moving but very energetic waves across is surface. The waves would be variants of Rossby waves which are triggered by the stress on rotating fluids. A tilt of just one degree with such waves slowly propagating across the ocean under Europa’s ice should create some 7.3 exajoules, the energy equivalent of 1.74 billion tons of TNT. In addition, the propagation of these waves would help Europa’s ocean churn, stirring up potential nutrients for living things.

Now, all those strong indirect hints that something very interesting and potentially living could be going on just a few miles under Europa’s ice should be taken with caution. We would only know if the moon can support an entire biosphere when we land on its surface and probe into its seas. Hopefully, something will swim up and wave its fin/tentacle/spine/antennae at the cameras, but we probably shouldn’t bet on it. Without seeing aliens outside movies and TV shows, we could easily miss something we didn’t even know was alive. There’s also a very real possibility of forward contamination, that is sending our bacteria to other worlds on equipment which we want to use to find alien microbes. In the worst case scenario, these bacteria will taint the samples, trigger false positives on lab tests, and be a real pain for the researchers trying to separate terrestrial microbes from extraterrestrial ones. Hopefully, life on Europa has more of a similarity to jellyfish and sea anemones so we’d be able to rule out contamination thanks to the sheer size of the life forms we discover.

And interestingly enough, liquid water oceans swimming with life aren’t the only kind of fluid that’s possible in the outer solar system. Deep in the innards of Uranus and Neptune, temperatures could soar above 50,000 K and pressures could reach between 6 and 10 Mbar, or in the range of 87 to 145 million psi. Under the extreme heat and stress, the carbon layers inside the gas giants would turn into diamonds, and not just any diamonds but a dense, metallic graphite fluid with chunks of solid diamond-like material. A thick enough layer of molten diamonds behaving like an ocean could also explain the bizarre tilts of the magnetic poles of the two planets since it would interact with the magnetic fields emanating from the core and deflect the lines that feed into the poles. Oh and just in case you might be wondering what it would be like to swim in a diamond ocean, don’t. At up to 40 million atmospheres and with temperatures about nine times hotter than the surface of the Sun, this ocean would crush your body into a tiny little clump as it vaporizes you with blistering heat…

See: Tyler, R. (2008). Strong ocean tidal flow and heating on moons of the outer planets Nature, 456 (7223), 770-772 DOI: 10.1038/nature07571

Eggert, J., et. al, (2009). Melting temperature of diamond at ultrahigh pressure Nature Physics, 6 (1), 40-43 DOI: 10.1038/nphys1438

We’ve brought up the topic of evolution and its role in astrobiology before when discussing how many aliens could evolve some sort of intelligence and how intelligent they could be, as well as what they might choose to do with their brainpower. Given the right environment and the potential for complex life, the ability to evolve what we would consider societies isn’t at all far fetched. Since there are so many worlds that aren’t hospitable to life in general, civilizations may be separated by vast distances and time scales. As one society is rising to power, the other may be in its decline and death, or vice versa. But even when we consider that, there should still be countless alien species out there, just itching to contact us in the dream scenario of alien hunters. To find out why scientists can’t seem to find them, we need to consider what exactly we mean by intelligent aliens since many of us like to use this phrase so casually, it’s become a very nebulous construct.

Many humans tend to forget that we’re not the only intelligent creatures on our own planet and may theologian navel-gazers use our lack of humility in this regard as proof of some sort of divine design. Why would there be only one creature endowed with the brainpower to understand its existence by random chance, they ask. If we consider that argument outside of a theistic framework, it sounds something like one of the comments in the aforementioned Daily Galaxy article…

There are about 1.5 million known animals, plants and algae on earth. Never mind bacteria and [any] as yet unknown species. How many of these have developed “intelligence”? Just one. I think life is rampant, but “intelligent” life is not.

I wonder why we’re forgetting about dolphins, apes, elephants, parrots, whales, squid and octopi? They’re all endowed with some sort of intellect and many scientists tend to hold dolphins as the second smartest living things on the planet in a very close tie with whales. If we go by what the theory of evolution predicts, there has to be a spectrum of intelligence in a wide number of species and depending on whether natural selection and key mutations have enabled a small number of species to capitalize on brainpower as a means of survival. By letting go of our egotistical notions of our superiority over the planet, we’ll notice that we’re not the only ones on planet Earth with some wits. How far ahead we are, we don’t know because there’s a still a lot to find out how smart some of the other species around us really are. And when we’re looking to other planets, their situation should be roughly similar. Maybe, there really are countless intelligent species out there, but they could never build spaceships or cities because they don’t have the right limbs or don’t have the conceptual skills because natural selection on their world limited the reach of their mental abilities?

Continuing to stray from the beaten path, let’s also think about what we would say to an alien creature. Some of us are desperate to talk to one while many are content to find them at our own pace rather than spend time, money and effort on the task. Do we really want to tell them our secrets? Do we want to send them everything we know in digital form? Would what we consider our great works of art and science impress, infuriate or just bore an alien society? Our cultural differences might be so vast as to be irreconcilable. We can’t even talk with each other most of the time, much less other intelligent creatures on our own world. Chatting with aliens who live quadrillions of miles away isn’t exactly going to be any easier and this may be why there are a whole lot of very smart and advanced civilizations who make it a choice to shun games of interstellar message tag.

The news editor at Cosmic Ancestry was doing a little write-up about the puzzling discovery of seemingly old galaxies in distant space. Since looking into the depths of space is also like looking back in time, this would mean that the galaxies aged prematurely. This is certainly an interesting anomaly that needs to be explained, but it’s hard to see the link between these results and the origin of life. And this is when this little gem reared its ugly head, mixing creationism and pseudoscience in a manner worthy of Answers in Genesis…

Most darwinists know little about the big bang, but rely on it to mandate that life must originate. In cosmic ancestry life never originates and must come from the infinite past.

Wait, what?! We have to throw out modern cosmology to accommodate panspermia? Since when? And aren’t we left with the same infinite reductionism problem we find in religion? Life had to come from somewhere, so just pushing it back to the ancient past and ignoring what the other sciences have to say about the universe to make it plausible, doesn’t work. Wasn’t the whole point that life gets started on one planet and eventually, due to chance, cross-pollinates other worlds and the evolution takes off in its new home? And speaking of that, do we really need to invoke an anti-evolution epithet favored by creationists? Isn’t alien life hitchhiking from world to world supposed to evolve in its new home, not just arrive as a pre-assembled ecosphere?

Here’s the bottom line. Panspermia can’t be the answer to the origin of life in general. It can explain how living things arose on a particular planet and is at best, an intriguing and potentially profound part of a much bigger puzzle. Whether it got there through incredibly tough microorganisms that made it to other worlds by everyday events, or as forward contamination by alien explorers surveying potentially habitable worlds, it will never give us the ultimate answer of how life arose. We can only find out with biochemical experiments and research. To use alien bacteria as the ultimate answer to the biggest question of biology is a religious tenant, not a serious scientific statement by any stretch of the imagination.

When we look at life as something that’s not a one in near-infinity event which happens only when conditions for are perfect, but as a series of persistent bio-chemical reactions, we can take a survey of our surroundings and note the immense amounts of raw ingredients for living things floating around stars and solar systems. There’s plenty of water as ice or locked up in minerals. Asteroids and comets are filled with amino acids and useful metals like iron, cobalt, copper and zinc. In young solar systems, these compounds rain down on new planets in vast quantities and when conditions are right, they can combine into new organisms. Applying the statistics mentioned above, it seems logical that life has many chances to spring up all over the universe.

Of course looking at life as some sort of interstellar virus that infects planets just doesn’t sit right with those of us who’d like to think of themselves as special enough to warrant the outmost attention of some supernatural being with immeasurable power. Then again, nature really couldn’t care less about our delusions of grandeur or whether we’ll ever fulfill our futuristic dreams. And realizing that we’re not the center of the universe and that life is just a function of complex chemistry is probably a good thing. It keeps us humble and lets us know that we have a lot left to learn about who we are, where we came from and there we’re going.

The big problem with trying to figure out just how hospitable the universe is to intelligent species is our lack of data about alien life and habitable planets. By this, I don’t mean just carbon based life on a planet with liquid water orbiting around 1 AU from a type G star. Planets that can be habitable to some organisms which will be able to achieve something we could classify as intelligence if given enough time, also count. But since we’re just now developing the technology to detect the presence of potentially habitable planets and it will take us a while until we have the means to examine any aliens for signs of intelligence (unless it’s made obvious to us by electronic signals or lights from vast hyper-cities on a planet’s surface), we can’t possibly start drawing up the statistical distribution of life in the universe and start making conclusions about it. But no matter what we ultimately find out, whether we find that intelligence is rare in the cosmos or it’s as common as dirt, a variant of the principle will be satisfied in some way, shape or form.

And even more interesting, we could show that there’s a wide range of physical laws which allow for life as we know it to come into existence and function, and we would be giving more proof to the variant of the principle which argues that we shouldn’t be surprised life would eventually appear, while weakening the variant which predicts a universal fine-tuning. Conversely, we could find a very significant restriction on the laws of physics or chemistry and do the opposite. And that makes me wonder why a single principle can be so contrary in its variations and remain a single principle. What exactly do you do with a theory that predicts something and its polar opposite at the same time? How do you test it, especially when it gives no fixed data points and leaves itself wiggle room no matter what you find in an experiment or observation? How do you apply it? Should you bother with it at all? Is it just a cosmological tautology?

I will make this correction to my original post; the paper was addressing a fine-turning variant of the principle which dealt with the realms of particle physics and quantum mechanics. So if you agree with the variant which says that we shouldn’t be surprised by comfortable ranges in the laws of physics, it gives the principle more credence. If you’re a fan of the fine-tuning idea born from theological musings on physics and chemistry, well you’re out of luck in this case and have to now move the goalposts to accommodate for these ranges. But that brings us right back to the question of how one principle can have contrarian variants and be both reinforced and weakened at the same time…

Imagine landing on Gliese 581d on the shore of a large ocean that’s supposed to cover a sizeable part of its surface. You would immediately feel two things. The first would be the tremendous gravity. A human ordinarily weighing 160 lbs would instantly get an extra half a ton heavier. The stress would be more than twice what astronauts on the space shuttle experience during lift-off to orbit. Since the human body can only deal with this much force exerted on it for a very short period of time, there are all sorts of serious dangers associated with being exposed to gravity that intense. Taking even one step would be impossible. Your muscles wouldn’t get any stronger to accommodate all that additional weight and trying to move hundreds and hundreds of pounds while the same stress is pushing you down would be a Sisyphean task.

The second thing you would quickly note would be the wind. Gliese 581d is so close to its star that it’s tidally locked. One of its hemispheres is always facing its sun while the other is always shrouded in the darkness. For a while, scientists thought that the dark side would be frozen solid, but recent studies suggest that a planet with a thick atmosphere would be able to circulate heat around the entire world. But the temperature differences would create powerful global windstorms. On tidally locked gas giants, the combination of hot air on the day side and frigid air on the night side fuels supersonic gusts. The weather would be much calmer on 581d, but its winds would still howl. You might also want to stay away from the equator. Constant heat over billions of years could spawn an endless cycle of major storms there.

Don’t be surprised if the sky’s color palette is muted. Gliese 581 is a red dwarf which emits most of the energy it produces as infrared radiation rather than as visible light. The exact colors depend on the gases that make up 581d’s atmosphere, something we don’t know yet. And speaking of colors, the ocean might not be blue either. Depending on what minerals saturate the water and what living things make their homes in its depths, safe from weather and infrared beams, it could have a very different hue. It’s at the bottom of these alien oceans that creatures could feed on by-products of volcanism and find an oasis on what’s otherwise a harsh and bizarre planet.

Now for the technical part. While the molecular structure of amino acids in all living things on Earth is wound to the left due to the potential influence from meteors that fell to our young planet as it was forming, not every molecule in our bodies has a left-handed chirality. Some compounds in our DNA are actually right-handed. So what good would it do to look for polarized light from an alien forest which would probably have both right- and left-handed molecules present in its basic makeup? According to the team, light reflected by photosynthetic organisms has a bias towards a particular chirality in stark contrast to various minerals used as controls in their experiment. Minerals have a fairly random distribution of chiralities and don’t polarize light as definitively as living things. Even water rich meteorites, which can have up to 18% more left-handed molecules, wouldn’t be as homochiral.

This homochirality is what an “astrobotanist” would try to find in the spectrum of light from an extrasolar world. Having a clear bias towards a particular handedness should be a sign of heredity and heredity is a sign of living things. With a strong bias to the right or the left coming off the planet’s flora or enormous colonies of microscopic fauna, we could safely theorize that we’ve found an alien biosphere. And since we’d be doing this light years away, we wouldn’t have to fret about cross-contamination tainting our data.

The idea of looking for photosynthetic aliens has been around for a while and was discussed in a Scientific American cover story which goes into another intriguing detail; the possible colors of plants on other worlds. On planets orbiting a very bright star, they could be blue to reflect most of the light they get. If they didn’t, they’d absorb too much energy and fry themselves to a crisp. Around small, dim stars, the picture could be very different with black plants trying absorb any light they can. Finally, around young flare stars, plants might need to be aquatic which would pose a big problem for telescopes. Water would alter whatever light is being reflected by the extraterrestrial flora and potentially interfere with spectrometry readings. Of course this is all based on our understanding of photosynthesis and that understanding is limited to one planet. There’s really no telling what a forest on a faraway planet would look like.

Originally, trying to give potential colors to alien plants was suggested as a quick and dirty way for an astronomer to figure out whether there might be something interesting on the planet’s surface when we can build telescopes powerful and agile enough to take snapshots of exoplanets. But the idea of looking for a chemical signature of heredity would skip the problems associated with guessing what photosynthetic alien biospheres would look like on a planetary scale and could make it easier to detect a more persuasive indicator for life than unidentifiable colored patches measuring less than a fraction of a fraction of a pixel at best.

See: Sparks, W., et al., (2009). Circular polarization in scattered light as a possible biomarker Journal of Quantitative Spectroscopy and Radiative Transfer DOI: 10.1016/j.jqsrt.2009.02.028

Natural selection dictates that only the organisms that can survive long enough to pass on their genes or whatever hereditary traits an alien might use, will be the only ones left. A fact that often gets ignored in these existential questions is just how many extinctions take place on a daily basis. More than 99% of all living things which ever lived on Earth alone, are now long gone. Many weren’t around long enough to branch off into new lineages and have descendants. Even today, countless organisms are going extinct and we somehow manage to overlook this systematic death, gaze at the stars and ask whether the whole universe is built to encourage living things. Isn’t it odd that our incredibly hospitable world managed to witness nearly all life that ever spawned on it die while we’re all busy discussing how suspiciously alive the universe must be?

Life, as we understand it today, is built on chemical reactions which help give rise to active, reproducing creatures. The environment of whatever world the living things in question call home will cull anything that can’t survive its rigors in a very short time. The survivors will thrive and spread, changing and diversifying as they do, at least until their environment changes and those unable to cope with the shift in the conditions will be culled again. If the universe is crawling with life, these are survivors, outcomes of countless evolutionary experiments on trillions upon trillions of worlds. The environment in which they live aren’t uncannily suited to life, much less to them. These organisms just happened to persevere.

We all know about the SETI project which listens for potential signals from aliens with radio transmitters and powerful lasers. But now there’s a new acronym to memorize in the search for otherworldly life: SETG. It stands for the Search for Extra-Terrestrial Genomes and its lead scientists want to do nothing less than find and sequence gene segments of microorganisms living under the surface of Mars. How? They’re betting that Mars and Earth share an evolutionary heritage and that will allow biologists to read Martian DNA.

Let’s rewind to the beginning. Around 4.5 billion years ago, when the planets were just forming and fusing into the solar system we see today, asteroids and comets rich with organic material rained down on the young planets and helped jump start life. As the collisions continued, some of this new life was exchanged between Earth and Mars and hence, by trying to analyze the 16S ribosomal RNA gene which is often used to identify bacteria and their evolutionary lineage, the project would not only prove that there’s recent Martian life, it would also provide evidence that life in our solar system, and indeed the universe at large, may be related. Or at least, this is the theory behind SETG’s plans.

Suppose that a Martian rover a few decades into the future carries a SETG machine which uses solvents and a special dye that glows when it binds to genetic materials. What kind of life could it find? To get a reading, the alien microbes would have to be no older than 1 million years old, the average time it takes for the DNA molecule to decay, use amino acids we know of and have colonies large enough to leave an identifiable trace in the sample. Oh and they would also need to be different enough that we call tell them apart from any possible Earth bacteria which could hitch a ride to the Red Planet and contaminate the results. And that’s where issues like chirality and the distribution of basic compounds for life make create a huge problem for alien hunters.

In a previous post, I examined a NASA study which shows that asteroids rich with water tend to produce a bias towards left-handed chirality, or when the molecular structures of amino acids used by every known organism wind to the left. A right-handed chirality in alien life forms is an exciting possibility and a sure-fire way to know we’re dealing with organisms that are definitely not like any living things we know of, but it has a lower chance of fostering a biosphere than the left-handed amino acids overrepresented in the very same asteroids crucial to SETG’s research and experiments. If we do find Martians to run through a sequencer, we may find that they and their Earthling counterparts are too closely related for a definitive identification. But of course, we have to find those elusive alien microbes first…

Let’s say that we land a robot on Europa and manage to slip a submarine into the ocean under its icy shell. Some bizarre being no one has ever seen before swims up to the camera. Well that would be pretty cut and dry. It’s living in an alien ocean, it moves, it’s active, so it’s obviously an extraterrestrial organism. However, what if the only living things in that ocean are bacteria and various slime? Maybe it’s not as warm and active as we think and complex organisms wouldn’t evolve there. When we focus our microscopes on them, would we be able to tell what’s living or what’s just a collection of organic compounds? What does alive mean on a microscopic level?

Believe it or not, we have a very similar dilemma right here on our planet. Viruses are abundant and they do a lot of things that all organisms on our world do. They reproduce, they mutate all the time and they evolve into new and different forms. However, until they can find a host with the cellular machinery to help them spawn more copies of themselves, they’re more like a ball of inert biochemical components. Their outer shells, or capsids, resemble crystals rather than cell walls and the genetic material they use for replication is sometimes like looking back to the very start of evolution, when hereditary materials were being passed by RNA rather than DNA.

It was usually thought that because viruses required other living cells to replicate, they must’ve evolved after the first microorganisms and persisted because they evolve so quickly. With their usually tiny genomes, very few repair mechanisms like the ones found in DNA and astounding amounts of copies they make, viruses exemplify natural selection at hyper-speed. But now, the experts think that viruses could’ve actually been one of the very first life forms and replicated in other ways until they could interact with other microorganisms. Their proof is the fact that a typical genome of a complex organism like a human has more viral genetic data that the actual encoding genes we use on a constant basis. Most DNA on Earth is basically legacy code from a wide variety of primordial and ancient viral mechanisms.

So if we land on another world, start looking around and nothing comes out to greet us, maybe we should focus our efforts on finding alien viruses as they’re replicating themselves. It would be a far cry from little green men with ray guns but it would still be an actual, living alien. Albeit living by technical definition only.

According to the math, our planet should be a snowball flirting with 0°C or 32°F temperatures all year round. While that’s warm enough for a lot of microbes to exist, complex life probably wouldn’t have evolved. Add to that the fact that the Sun was actually much colder a billion years ago than it is today and it seems that without greenhouse gases, Earth would be a frozen desert. Clearly, there’s a major problem with using the distance from the star to determine the habitability of a planet. With the recent launch of Kepler to look for other Earths in other solar systems, we need to keep that in mind and develop a much more precise approach to figure our whether life like we know and understand today could evolve on one of the planets we’re bound to detect, and give climate its due as a key player in the evolutionary process.

This is exactly what an interdisciplinary team of scientists said in a 2008 paper on the subject of life on alien worlds. Without directly rebuking the habitable zone concept, they pointed out a wide number of flaws which have to be taken into consideration when a new planet which looks like a potential habitat for extraterrestrials is found. For example, if the planet has a very thick atmosphere and high pressures, water remains liquid at temperatures above 100°C since the boiling point of water on Earth is based on the pressure of our atmosphere at surface level. We can see examples of this phenomena in ocean trenches where volcanic eruptions can’t boil the water around them due to the immense pressure on the bottom of an ocean.

The team also outlines biological considerations. We know living things that feel comfortable at temperatures we would find to be inhospitable. Bacteria can live in -85°C while some strains of archaea could withstand 130°C and reproduce at -10°C and 121°C respectively. Sure, it’s not intelligent, complex life that many space enthusiasts and sci-fi fans want to find, but it’s life by all existing definitions. Because we don’t really know what alien life is like, we can’t rule out that it may be even tougher that that. After all, natural selection on an alien planet would do its part in weeding out organisms that aren’t efficient enough to thrive in harsh conditions.

But the most important aspect of their work is pointing out that seasons and regional climates would play a major role in influencing the planet’s habitability. How well does the planet hold up to an ice age? In an ice age, is everything frozen or are there places where temperatures would be nice and warm for complex life? Understanding the dynamics of climates on an alien planet, the long term trends of its orbit and the duration of its seasons are all major factors in making a case for a specific kind of life on a recently detected planet. Casual eyeballing of where it is in relation to its parent star just won’t do for planets other than our stellar twins.

See: David Spiegel, Kristen Menou, Caleb Scharf (2008). Habitable Climates The Astrophysical Journal, 681 (2), 1609-1623 DOI: 10.1086/588089

Though reported as a novel oddity, Funes’ thoughts on alien life and their relation to the Bible are an important indication that sooner or later, the world’s religions will have to address the concept of alien life. Even a few decades ago, organized religions could get away with absolute silence on the subject. It all seemed so speculative, so far away and so improbable. But things have changed in this millennium. The idea of finding aliens any day now is exploding from the headlines and whether a planet or a moon is a good candidate for an alien habitat is invariably being asked with each new exoplanet and each pass through the outer solar system.

When the search for alien life is making daily headlines, it seems like a good time for religious institutions to start delivering some opinions on aliens and how they fit into all the dogmas and doctrines. It’s an important preemptive act because the discovery of an actual Martian microbe, for example, could make many of the world’s faithful start wondering why their holy books say nothing about life on Mars or on any other planet. That’s especially true in the West, where the Vatican feels that it has to embark on campaigns discouraging secularism and large groups of fundamentalists are trying to get more and more political control to legislate their ideology on the grounds that too many people disagree with them and are losing touch with their faith.

Another interesting tangent is where the discovery of life on Mars would leave creationists who argue that there’s no way that life could survive in a cold, harsh habitat and needs a caring and advanced deity to care for it and make it more and more complex? As some commenters on PZ Myers’ blog noted, even alien life wouldn’t damper the spirits of hardline creationists. They could point to the fact that for all intents and purposes, life on the red planet couldn’t evolve in complexity which proves that without the hand of a creator, macroevolution is impossible. No need to note that the environment wouldn’t allow more complex creatures to survive and that’s the best Martian life can do. That brings up that pesky natural selection thing which creationists like to attribute to terrible historical events and thus reject it on ideological grounds alone.

They could claim that germs from our spacecraft contaminated the surface of the planet and it really isn’t the discovery of life as much as proof of divinely ordained panspermia. It’s possible but the harsh UV rays and bitter cold that sterilize the top few inches of Martian soil where our robots operate, would kill pretty much anything from Earth. Even if a few microbes did survive, they wouldn’t have time to grow fast enough to establish a planet-wide methane cycle. If you’re thinking of how the discovery of aliens on our planetary neighbor would cool the jets of ardent creationists, you might want to adjust your expectations accordingly. Same goes for icy moons of gas giants. The harsher the environment, the slower the evolution and the louder the cries of protest.

Since we knew that Mars was a sphere of rock, we assumed that it may be habitable which is a big part of the reason why we’re investing billions of dollars into scanning the planet for even the tiniest hint of life. So far we know that Mars was once wet and recently, we’ve had a whiff of methane that may or many not be produced and replenished by Martian microorganisms. The problem with making a definitive call is the fact that methane can be produced by bacteria and geological processes and until we uncover a sample of actual Martian microbes, all we have are educated guesses and possible scenarios. The rovers on the surface of Mars couldn’t to go to the epicenter of the methane emissions and start looking for life. They’re just not designed to do that. An exhaustive search for microorganisms would be done a lot faster and much more efficiently by a human mission to the red planet.

Our search for life on Mars brings up an interesting question. Is life a rare thing which would only happen if and when all the ingredients are right for it, is it like a virus which tries to make a home out of anything even remotely capable of sustaining a living organism or is it something in between these two extremes? Take early Earth. Around 3.5 billion years ago, when we finally see a fossil record of something which resembles living things, the conditions on our planet’s surface were extreme to say the least. Hyperactive volcanoes, enormous lava flows, boiling hot temperatures, the beginnings of what would become oceans glowing green with iron and other metals, constant impact events and an atmosphere choked with toxic greenhouse gases. And yet, basic organisms clung to life in what we would describe as nothing less than hellish.

But they didn’t grow or develop in complexity. They couldn’t. More complex forms need more room, more resources and a more stable climate to survive. Environment dictates the direction and the pace of evolution and until approximately 600 million years ago, the harsh climate of a fiery and oxygen starved Earth put the breaks on the process. Only a few microscopic changes could occur. As soon as the global climate stabilized and bacteria which fed on carbon dioxide and oxidized the iron in the early oceans, helping to raise the oxygen content in the air to some 20%, life started getting more complex and elaborate as more and more complex living things could survive and pass on their genes to the next generation. Life on our planet seems to act a lot like a virus, trying to expand into any available niche to reproduce itself.

So if we adapt the same view to Mars, we could use the detection of a methane cycle to say that there’s no reason why there shouldn’t be life on red planet. After all, it’s not like there we don’t know of any bacteria which don’t need oxygen to fuel their metabolism and give off methane. We have colonies of these microbes right here on Earth. And if life managed to survive on our toxic and dangerous environment billions of year ago, why not on Mars? Maybe life is like some sort of inevitable virus? All the ingredients for it are abundant in comets, asteroids and nebulae across the known universe. It’s just a matter of time until it rains down on a young planet and starts bonding into organic molecules, right? Unfortunately, until we find a Martian microbe to study in a lab, we will never know for sure.

If we want to visualize an alien, we’ll have to think about its chemistry and its environment but we also need to allow nature to impart its messiness and imperfections like vestigial organs or bizarre shapes. One of the main reasons why the iconic little gray men are so much like us, is our desire to relate to alien species. Making them look very similar to humans, gives us some degree of familiarity with what should otherwise be a totally confusing creature we would know nothing about. But when it comes to the science of the matter, we need to throw away our ideas about intelligence and aesthetics. Since intelligence is an evolutionary fluke, aliens are probably going to be feral animals. Because they evolved on a world with different conditions from ours, other kinds of body shapes and designs might have been better for survival.

The creature above, the Groveback from Wayne Barlowe’s project Expeditions, is perhaps one of the best guesses we can have as to what kind of aliens we might encounter on other worlds. During his education, Barlowe worked on illustrating natural history, serving an apprenticeship in the exhibitions department of The American Museum of Natural History so when he draws an alien creature, he’s applying all the rules we just talked about. That’s why his designs seem to be so plausible and provide a much better model for visualizing extraterrestrial life. Want to see what an intelligent alien might look like? Forget about the little gray men. An Eosapien is a much more accurate concept.

So the next time you hear one of the many stories about humanoid aliens flying around, taking random people aboard their spacecraft for sinister, invasive or downright sexual experiments and just generally scaring the living daylights out of a local populace, find a concept sketch of something like an Eosapien and ask yourself if you’re ready to imagine such a creature floating around, pushing touch screens and buttons with its tentacles and humming out instructions. In fact, try it right now. How does it make you feel? What do you prefer? Little gray men or eerie tentacled monsters with similar brainpower?

However, when theists positing this argument focus on dissecting the hopeful anticipations of many space enthusiasts and scientists, they miss a very important snag in their theory. Yes, alien life is a belief at this point, not fact. But this belief is based on the probability that on some faraway planet, somewhere, abundant organic ingredients will eventually combine into a living thing. We’re not even talking about intelligent life since intelligence is more of an evolutionary fluke than some sort of mandatory requirement for survival. We’re just talking about bacteria and very simple animals.

Compare an odd bacteria living on another world to an omniscient, omnipresent and immortal being that not only created our planet, but all of existence. Which one seems more likely? Oddly enough, when I offer the idea that a sufficiently advanced alien race could be mistaken for gods and that they could’ve created life on a far off planet as an experiment to test their theories, like we’ve done this year, I’m met with either silence or varying levels of resentment. I crossed the fine line between theology and science, and entered the realm of heresy.

My stance on the ancient astronaut theory, the idea that aliens created humans and our entire civilization, is that it’s highly unlikely and very improbable. But you could find enough ancient artifacts of extraterrestrial origins on Earth or the Moon to prove that alien intelligences had a role in our development. Granted, the burden of proof would be enormous. You’d need to find not only alien spacecraft but tools meant to design living things and proof that they were used to develop something found on Earth today or in the fossil record. However, improbable and very difficult don’t add up to impossible. And here’s where belief and skepticism differ.

For a believer, the very fact that something isn’t impossible is enough to believe it. Skeptics on the other hand want to see the tangible proof before they commit to an idea. The fact that it’s not improbable simply means that it’s an interesting idea and if there’s any evidence to it, they will certainly want to check it out. I place myself in the second camp.

Our search for life on other worlds is about heat and water. Since we only know one type of life, the creatures that inhabit our planet, we’re narrowing our focus on environments that seem to resemble our own. So far, we have a promising result. Gliese 581c and 581d are rocky worlds, much bigger than our own but with the right conditions, extremely hospitable to pretty much everything from bacteria to complex animals that could evolve to overcome the high gravity. Even intelligent life isn’t out of the question and all that is only 20 light years away. When we’ll launch the Terrestrial Planet Finder in 2015, who knows how many other promising places we might find in a hundred light year radius.

However, even if we do find that our planet is pretty common and space around us is rich with nearly perfect habitats for life as we know it, we could still be missing something important. If we want to get a true idea of how widespread life in the universe really is, we need to consider other forms of life and different kinds of organic chemistry. In fact, while we’re spending a few billion dollars on searching for life on Mars, other places in our solar system might be better destinations for an alien safari. Chemistry doesn’t stop because it gets cold. It just takes on a different form. Moons we consider icy wastes could be teeming with life by relying not on heat, but on extreme cold and if they’re included in the final tally of habitable environments, they’d change how we see the distribution of alien organisms across the cosmos.

It all has to do with solvents. Life needs three things. Organic molecules that can combine into a working mechanism, something that can be turned into energy to maintain the mechanism and let it reproduce, and a solvent to help the mechanism build the chemicals it needs. On our world, water makes the perfect solvent. It’s liquid and non-reactive. On another planet, where water would quickly be frozen as hard as steel, another non-reactive liquid could take its place. In our solar system, Saturn’s moon Titan is a perfect example of a world where living things could be using a very different solvent with the same result.

Titan is a pyromaniac’s dream. Or rather it would be if all the flammable material that the moon is made of wasn’t frozen to -290F and there was oxygen in the atmosphere. Otherwise, it’s very much like Earth. It has volcanism, oceans, lakes and an active ecosystem where all the organic materials and solvents alien bacteria would need for food and metabolic processes are being recycled and exchanged. Organisms on Titan could be using liquid ethane in exactly the same way their counterparts on Earth use water. At those super-chilled temperatures and without oxygen in the air, ethane becomes a non-reactive fluid.

So what does all this mean for our efforts to find aliens? Maybe rather than devoting all of our resources to looking for underground bacteria on Mars, we should be looking on Titan and on the more conventionally promising habitats of Jupiter’s Europa. By spreading our search across multiple worlds and by considering different organic chemistries, we stand a far better chance of finding aliens than we do by betting it all on one planet. On top of that, finding alien bacteria which use totally different chemistry from their Earthly counterparts would make it a lot easier to prove that we discovered a bona fide extraterrestrial and not just some bacterium that hitched a ride on the spacecraft sent to the habitat in question. After all, our germs have survived on another world once before.

For example, take a recent simulation of whether bacteria could survive on Mars. Although the article acknowledges a number of problems with how the finding that Martian soil under a few surface centimeters is habitable was made, it glosses over an important fact. We don’t know if an alien life form could survive on Mars. We don’t know what one looks like, on what it feeds or how its internal structure works. We could’ve come across aliens on Mars and Titan already and are totally oblivious to the fact. What this experiment proves is that some Earth bacteria under controlled Mars-like conditions could survive for a short period. It brings us no closer to alien life or answer how we would find it. We already knew to dig underground.

Now don’t get me wrong. We should be running experiments on what forms of chemistry will yield viable life. But when it comes to answering big questions like how we would actually find a living thing on another planet, we can’t rely on a simulation or experiment to give us the right answer or guide us down the right path. We don’t know enough about the aliens or their worlds to figure it out in a few meetings and with some beakers, test tubes and a computer. The only way we can do it is by going there, looking and trying to figure it out ourselves based on what organic chemistry we know might yield something viable.

But the habitable zone is a concept that applies only to the living things of this planet. Alien life could be a lot tougher. For example, it’s plausible for some alien bacteria to use liquid ethane instead of water as a solvent and live in -250F weather. Heat is a bigger problem because very few usable solvents can stay liquid at very high temperatures, but alien life forms could just do what animals on our planet do when it gets too hot for their tastes. They could hide in a cooler, darker place where the heat can’t reach them and it’s cold enough for water to stay in its liquid form. In both cases, the planets they inhabit could be out what we think is the habitable zone of a given star. But then again, the habitable zone is supposed to be a quick and dirty rule, not an authoritative ruling on the possibility of life for an extrasolar world.

On top of that, habitable zones are actually measured in hundreds of millions of miles. A little closer and a little farther are relative terms. For our solar system, the habitable zone would be between the orbits of Venus and Mars. That’s a band some 200 million miles wide. Our 12,700 mile wide planet has a whole lot of room to wander and still host life. If we include an alien that can use super-chilled liquids in our estimates, the habitable zone swells to over a billion miles. As you can see this is a pretty vague concept based on woefully incomplete knowledge.

However, this didn’t stop the concept’s creators from making a galactic variant. Apparently, a galaxy also has a habitable belt around its midsection. Too close to the galactic center and the radiation from the black hole and colliding, hyperactive stars will doom all life on a planet. Too far away and there wouldn’t be enough metal to form rocky worlds in the dark recesses of the galaxy. I can understand that you wouldn’t want to be too close to the galactic center. After all, there’s a supermassive black hole there and whipping around it are large, chaotic stars. Stellar explosions are common and huge gamma ray bursts could fry an otherwise habitable planet into a lifeless rock.

There’s also a problem with the chemical composition of planets on the edge of a galaxy. Stars migrate, moving around as they spin and when tugs from other stars, nebulae and black holes pull and push them around. Supernovae, which make metals in the final moments of their lives, scatter the atoms they produce across thousands of light years. The entire galaxy will be awash in all sorts of gases and metals given a little time. Relatively speaking of course.

So what are the chances that Earth is in the right spot in the galaxy and in the right spot around its parent star to host life by chance alone? Actually, very good when we consider that our star can safely wander in a swath over 25,000 light years wide (that’s 150 quadrillion miles) and our planet has an almost 80 million mile margin of error either way, conservatively speaking. There is a little disclaimer though. Different temperatures would drive the evolution of different kinds of life so while we wouldn’t survive being more than 80 million miles closer to or farther from the Sun, other living creatures could.