We humans are a strange people. Well, actually, we are the only people.
Man has never mastered intergalactic travel, nor has he enslaved a planet for its resources. Indeed, we have never even made contact with another race of intelligent beings, even for the most piddling of invasions.
Thus we admit that certain species may wish not to accompany such a sad species as humanity on the annual cruise around the Sun that each one of our current flatmates attends. Therefore we shall examine the varied non-Earthly living options of extraterrestrial life, before probing them and stuffing them in a tank full of green slime as a good article should.
Thales is widely credited as the first person to consider extraterrestrial life as a viable option, owing to his “water as first” principle. Unfortunately, the Greek realised that in Aristotle's geocentric universe, life would still be drawn back to the Earth to receive useless birthday gifts from in-laws, and hence concluded that true extraterrestrial life was nigh on improbable. The dejected academic thus did the only other thing an elderly man could do, and cursed the youth by inventing the high school geometry question.
Hindu thinkers charted such an idea earlier, with cosmic pluralism a theory explaining the limitless desires of the universe, however Western history has tended to get these mixed these up with the menu from the local take-away. Similarly, while the Talmud also states there are over 18,000 separate living options, being the Talmud, this was probably in reference to the ability of Jewish grandmothers to track you down and make you feel guilty in any world.
edit Early modern
During the Middle Ages, extraterrestrial life fell back out of favour in Europe as belief in even a single world worth inhabiting was questioned by the plague afflicted inhabitants.
In a 16th century dialogue, Giordano Bruno affirmed that the Earth was simply one of an infinite number of worlds that may be inhabited by life. For this belief he would be charged with heresy, vehicular heresy and heresy across state lines, but thankfully Giordano had good lawyers and was able to plea-bargain these charges down to garden variety sodomy. However he would still be executed in the manner most befitting a believer in pluralism between diverse communities: Giordano died while trying to make small talk over a barbecue.
Concerned by the weight of baroque literature theorizing societies on other planets, The Vatican issued a papal degree that "...one sin-filled world was quite enough for Jesus to save, and he probably doesn’t want to go through the whole cross thing again just because some microbes want a methane based atmosphere, thank you very much." The words are ours; however, the Papacy could be relied upon at that time to deliver a child-molestation-scandal quality denial of anything vaguely scientific.
With the further development of the telescope in the late 19th century to more closely document the barren and gaseous compositions of the larger planets, scientific discussion took on the thought process of a typical home owner and concluded that our particular address was exceptional. The general public embraced the idea that our planet was worth more than the average rock in the stellar neighbourhood, due in part to works such as H.G. Wells' 1893 War of the Worlds, in which the humans vanquish invading Martians. This was accomplished using the time-tested tactic of inadvertently giving them fatal diseases.
Indeed, like the heads of a homeowner's association, physicists have endeavored to establish an exhaustive list of strata regulations, or laws of nature, by which all tenants of the universe should abide:
- Keep the speed of light below 300,000m/s, especially after 10pm.
- Remember there are exactly 92 building materials permitted in this dimension.
- No singularities on the premises. They leave horrible messes on the couch.
You can't take a single picture of the Martian surface without at least one scientist telling you five little words: "Proof of life on Mars." This quirk isn't some prank that inexplicably became popular among the uncreative, either, because people have been doing it since 1854. And by "people" we mean William Whewell, the man who invented the word "scientist".
edit Favourable conditions
As you are reading this, we assume you are neither being burned to the extent of a sausage on an Australian barbecue, nor being frozen at the temperature of a corpse in a cryonics lab. That is because Earth orbits in the "habitable zone", the region around a star at which the temperature is between 273 and 373 Kelvin. So too does Mars, sometimes. This means that any life on the red planet would escape a death you may expect to see as a final move from Mortal Kombat.
Indeed, if you tried to write a complete list of everything that suggests life may exist on Mars it would be longer than Lindsay Lohan's criminal record. With that in mind, concerned scientists have directed their search based upon two patronizingly simple base ideas. Honestly, these ideas are best explained by referring to another extremely hardy form of life that continues to evade the authorities.
Life requires water like Rambo needs a weapon. Give Rambo a pebble and he can take down a small dictatorship; give cellular life the solvent for its biochemical reactions and it can rule a planet. Unfortunately the, how do we say, Russian soldier among the pigeons for Martian life is an exceedingly low atmospheric pressure, one that would prevent water existing for any longer than a few minutes before it sublimated into gas. Without water the organism doesn't start existing in the first place, which is kind of like if Rambo took a pass on the whole war in South East Asia to knit a scarf with a compound bow.
The six wheeled cousins of Wall-E, the Mars Exploration Rovers, discovered a big load of hematite in 2004. If you have ever been to a gem fair you would know that hematite is to water as regrettable sexual encounters are to alcohol, as in the former basically wouldn't happen without the latter. Buoyed by this fuck you to barometers everywhere, NASA announced the Mars Global Surveyor had found changes in craters and sediment deposits that could only have come from liquid water, leading to the hypothesis that Mars once had seas and rivers. Again in 2008, the Phoenix Lander confirmed that subterranean Mars was like a massive Popsicle around the polar regions. So there is water, yes, but we aren't anywhere near slapping a wet floor sign on Mars in the near future.
edit Organic chemistry
This whole search for water thing is, of course, plan B. After all, the single biggest collection of water in the known universe is currently neighbor to a black hole, and we are yet to hear of any logical train of thought that lands you on the same street as a feeding singularity.
Plan A is actually finding the chemical signatures of life. Life as we know it just can't help but leave a trail of organic residue, kind of like how our old metaphor Rambo leaves scattered about the charred remains of helicopters and other things that make communists dirty up their little red boxers. We can't so much as breathe without dirtying up the atmosphere to the extent that robots can trace our biotic makeup several thousand years in the future.
Indeed, the two Viking landers grabbed this search by the balls in the form of the Labeled Release experiment. The desire to pour X on Y and see what happens is something you get over when you receive a detention on the first day of high-school chemistry, however, that is essentially all the experiment involved. We cannot confirm whether the probe was readying a "Kick Me!" sign for the back of any potential Martian race when it poured a nutrient solution tagged with 14C over a section of the Martian soil and sat back to observe whether 14CO2 was produced, but it does get you in the mind of those working for NASA at the time.
In a victory for pubescent curiosity everywhere, enough of the desired gas streamed out to get all of the scientists involved high as a kite, at least until their second attempt at the experiment failed the next week. Giving the potential Martian species a few Miller–Urey nutrient compounds would have been like dropping a cake shop in famine struck Somalia, so expecting the organisms to not have simply exploded from eating was placing a little too much trust in a notion of self control alien to man. Needless to say, the findings were inconclusive, which is about the saddest adjective you can use when describing something scientific.
Oh look, I'm levitating. Gravity was inconclusive.
Either way, Mars has a little too much methane to be explained by geothermal origin. Seriously, absolutely no one can explain 99.2% of the methane created each year. For perspective, if you were to tell your girlfriend that you couldn't explain where 99.2% of the lipstick on your collar came from, she would totally suspect something was up. Mars is no different.
Thus far we have concluded that Mars has water with a "but..." and organic chemistry with an "if..." Unfortunately, it also has an atmosphere with a "fuck..."
The atmosphere is too thin to allow for the warming effects seen on Earth, hence the absence of liquid water. Atmospherically, Mars tends to be fairly unstable and the planet often experiences large dust storms. These global climatic events mean life on the surface of Mars is very improbable. Its climate makes the staple of all conversations, "How’s the weather been?", even more pointless and brings the day closer when everyone who says that can be stuffed head first into a crater.
Life should have taught you by now that a calm man is a dangerous man. He is a man more dangerous than the one swinging a shark. That is, because a calm man is a man hiding something. Possibly a bigger shark. As you see, it is always the meditating old kung-fu master concealing the most kickass moves.
Europa, a moon of Jupiter, is one of the smoothest objects in the solar system. This is due to a subterranean sea hidden just underneath the chilled surface, one that may deliver a foot to the face of contemporary microbiology. The oceans of Europa may hold an oxygen concentration greater than seas on Earth. So Europa may not only support aerobic organisms that survive on dissolved oxygen, such as fish, but ones larger than those on Earth. Need we remind you of a certain film franchise featuring a fish to illustrate just how dangerous Europa could be.
Of course the sheer wall of ice above the ocean would take a metaphorical shit on any photosynthesis-based ecosystem, unless there were another source of energy for those organisms at the base of the food chain. You know, like nutrients flowing from the very bowels of the rock.
In case you are unaware, Jupiter is so fucking huge it probably wouldn't even need a fake ID to pass itself off as a star. Jupiter has more gravity than a kitten has cute, and is about equally as good at making things act all mushy, things such as the mantle of Europa.
This liquid rock does what liquid rock does and generally blasts the crust of the moon more than Wiley Coyote on the average weekday, leaving the whole goddamn sea floor covered in black smokers and other features that were named in a less politically-correct time and place. Chemical disequilibrium created at such locations on Earth has been observed to support vast dinner parties of complex bacteria, as they oxidize nutrients and discuss recent enhancements of their organelles. This self serve buffet of sulfides would form the very bottom of the food chain leading all the way up to the biggest what the fucks that could haunt your nightmares.
Also, some scientists speculate that there may be subterranean species inhabiting Europa, such as earthly endoliths, a form of life so underground you probably haven't heard of it.
If life is a box of chocolates, then extraterrestrial life is also a box of chocolates.
And, as in any true box of cocoa based goods, there will be that single, melt-in-your-mouth, double-fudge, triple-bypass candy, wrapped so tightly it seems to disapprove of your mind even passing over the idea of consuming it. That candy is Titan.
When all the other moons were getting stepped on, Titan was chugging the atmospheric equivalent of the protein shake and pulling reps. The sixth moon of Saturn is the only moon to hold a thick nitrogen based atmosphere, like Earth. We say like Earth, because mentioning that Titan has a surface pressure about 1.45 times that seen on Earth makes us feel mildly inadequate, and announcing the fact the atmosphere is also far more extended just sounds like a poor attempt at innuendo.
Confronted with this overwhelming display of moonhood, the answer of the University of Arizona was to run a massive electrical charge through a combination of gases analogous to those in the Titanian atmosphere, because science is indistinguishable from a cheap horror film. As if crapping out everything you need for abiogenesis except for a birth certificate wasn't enough, this was the first time either the five nucleotide bases that form DNA or amino acids were found in an experiment without liquid water being present.
Titan's atmosphere is so thick that the surface observes an almost perpetual night, receiving up to 1% of the sunlight we experience on Earth, or 101% of that seen in Britain. This absence of light means the satellite is perfect for at least some forms of theorized life. Yes, we mean vampires. If this is the case, then the rainbows may only be the second most flagrantly homosexual things that form naturally on Titan.
Once one breaches the gaseous mother of all security systems, and gets used to knocking on the door of absolute zero, the surface of Titan is actually comparable to a youthful Earth. The geographic features of Titan would be familiar to earthly species, including exceedingly shallow gradients as the offspring of taxons with stock portfolios experience here on Earth.
The satellite features the only other truly stable bodies of surface liquid in the solar system, vast lakes of hydrocarbons that are tended to dutifully by teams of brown ethane clouds that remain mostly hidden from higher orbiting bodies. Study of similar terrestrial habitats suggests the ethane pools are a potentially golden location for the genesis of life, particularly if no one bothers to use the net before they enter. Flows of ammonia based lava also track across the surface in places. Unfortunately, these flows from the craters of cryovolcanos are entirely incapable of supporting life, making them suitable only for family fishing trips.
edit Gliese 581
The grass is always greener on the other side. In the case of the four to six planets surrounding Gliese 581, a star that forms part of the scales of Libra, we mean the other side of the galaxy.
In truth Gliese 581 is a red dwarf named after a phone number and stuck in the zodiac equivalent of a household appliance. However, the system does have the three planets with the conditions most similar to those empirically known to harbour life. To translate the words of an astrobiologist into understandable terms, that means the universe basically copied Earth and then clicked the paste button a few too many times at the corner of the galactic screen.
What is currently known about the Gliese 581 system is the scientific equivalent of a vague recommendation from the one sunburned friend with a tank top advertising a foreign lager. Indeed, like everything recommended in a Lonely Planet guide, Gliese 581g may not actually exist at all. If g decides to exist, then three of the planets reside at a distance to the star where organic compounds may be found in a stable state. Finding these chemicals would be more enjoyable than any family holiday, as the exceedingly racist sounding blackbody surface temperature of Gliese 581c is thought to lie between that of Venus, the world's favourite example of a runaway greenhouse effect, and Earth, the world's favourite world.
Right now scientists are just speculating about what the surface of the planets are like, so you can believe whatever floats your boat. Liquid water, we mean. When coupled with the greenhouse gases of the atmosphere, the active geophysics of Gliese 581c and sister planet d could permit an Earth-like water cycle. So essentially our quest for extraterrestrial life has turned into a search for a group of wet and wild siblings on the internet. Oh well.
All extraterrestrial living options are set in over 13.7 billion verdant years of The Universe (fig.1), which itself is within walking distance of all matter currently in existence. Except for the complementary parking.
If you desire any further information on extraterrestrial life, please address it to us in writing, preferably on a correctly stamped cornfield. We don't actually know what it says but we do appreciate the effort.