Extraterrestrial life, if found, is expected to be strange and astounding. But what if the feeling we experience following this amazing discovery isn’t excitement, wonder, or even fear – but one of déjà vu?
When I was a kid, one of the more thoroughly enjoyable films that my cousin, sister, and I frequently watched was Planet of Dinosaurs. This movie has something of a cult following today and the title really says all that you need to know. Of course, you don’t need to recreate dinosaurs in a laboratory if there’s a planet teeming with these beasts close enough for us to take a spaceship (packed with really snappy space outfits) and arrive in a relatively short period of time.
Set well into the future, the crew of a disabled spaceship crash-lands on a distant planet remarkably similar to Earth. Much to the dismay of the survivors, this planet, determined to be younger than Earth, is inhabited by dinosaurs (or, at least, creatures that really, really resemble dinosaurs). Some of the dinosaurs are less than hospitable to the newcomers and, ultimately, the human characters are forced to get really creative to dispatch the local Tyrannosaurus (this Tyrannosaurus was made out of clay). I really shouldn’t make joke of that – this film won the 1980 Saturn Award for “Best Film Produced under $1,000,000”. Special recognition was given to the films stop motion effects, which heavily involved the use of clay models.
This seemed to be almost ideal for me. As a child, I loved dinosaurs (I still do) and would have loved to travel the galaxy to see the sights (I still would) – especially if there were dinosaurs out there (please let there be)!
Of course, I spent the next two decades of my life hearing that extraterrestrial life would almost definitely not consist of dinosaurs. Or giant bugs. Or little green men. Or even little grey men. A countless number of researchers and scientists have offered a similar reality: we can’t possibly begin to imagine the shapes and forms extraterrestrial life might assume. There have also been plenty of suggestions from the scientific community that extraterrestrial life may be unrecognizable as life to mankind.
Then Planet of Dinosaurs came roaring back. A recent study suggested that Earth may have been seeded with life by a meteorite billions of years ago. This meteorite would have brought the chemical building blocks for all life that has ever existed (sans perhaps just a few bacteria) on Earth. Where there was one meteorite, there may be been two, or a dozen, or a hundred. Planets across the Milky Way could have been seeded with the same amino acids and sugars. If the mixture occurred elsewhere in just the right way, however unlikely, there could be dinosaur-like creatures roaming around on a planet in a nearby star system.
Although the dinosaur part really appeals to me in a nostalgic way, that’s not what is worthwhile to me about this study. When I first read this (and later, similar, research), my initial thought was “if there is life nearby, maybe it’s a little more similar to us than expected.”
This goes a step farther. Earth, having life genuinely created here or seeded from the cosmos, could have, in turn, spread the proper organic necessities to some very close neighbors. There is a term for this possibility: lithopanspermia. Rocks harboring microscopic life from the Earth could have been ejected by meteor strikes into space eons ago. These rocks may have subsequently struck other bodies in our solar system. Lithopanspermia, of course, remains unproven as a means of spreading life from one planetary body to another. There is no firm evidence that microorganisms could survive a journey through space.
However, a study from Pennsylvania State University has demonstrated that, over the last three billion years or so, somewhere between one and ten rocks ejected from the Earth has struck Europa. Europa, one of Juptier’s moons, is the favorite darling of those believing extraterrestrial life may be found somewhere in our solar system.
Imagine now a rock (or rocks) from Earth, carrying early indigenous (and very simple) life forms, smashing through the ice on Europa and plunging downward in the massive ocean dominating that moon. A popular theory holds that life originated on Earth near deep-sea vents that seeped valuable mineral content and heat into the ocean. Such vents are also believed to exist on Europa. Our Earth microbes survive their hypothetical space journey and settle to the bottom of Europa, introducing life to this new world and continuing their evolution – perhaps with a subtle twist or two.
This serves as a critical plot point in Dying Up There. Set several decades in the future, the protagonist, Mark Helling, is a crew member of the first human expedition to Europa. The search for extraterrestrial life has ended, but this meeting isn’t a discovery as much as it’s a reunion. What Helling and his companions encounter might seem strange, but there’s a discomforting familiarity present. After all, the human characters and this newfound entity are made of the same stuff – each have origins in the same primordial soup found on Earth eons ago. Both grew apart over the eons, but they go way back – for better or worse.
How will extraterrestrial life look if such is found? I am still caught up in the idea of “alien dinosaurs“. Are those out there somewhere or what?
Does the chaos or hidden corners of the universe frighten you? If not, maybe it should.
Cosmophobia is a fear of the universe. This phobia includes an excessive unease with the sheer enormity of space, the relative insignificance of oneself when compared to the vastness of the night sky, and the inherit dangers, both known and unknown, therein. Whether or not humanity should have a fear of the cosmos is one of the main ideas within my current writing project, Dying Up There. The protagonist of this piece has a few Earth-bound fears, but will he learn to dread what the cosmos is hiding most of all?
Among the many fears of humanity, one may very well assume that cosmophobia is considerably down the list. Phobias are extreme or excessive fears, and fear is, by definition, “an unpleasant emotion caused by the belief that someone or something is dangerous, likely to cause pain, or is some kind of threat”. Many “common phobias” are quite widespread throughout the human population and, arguably, for good reason.
In many cases, these root fears transcend age, race, and creed. Those phobias common within the general public include (but are certainly not limited to): acrophobia, a fear of heights; astraphobia, a fear of lightning; and pyrophobia, a fear of fire. However, these fears may be justified. Falling from excessive heights, lightning strikes, and uncontrolled fires are all deadly and our ancestors undoubtedly encountered these dangers more often than the average person does today. Thus, a foundation of fearfulness of these examples was laid long ago.
Acrophobia (fear of heights)
The dangers presented by a rocky seaside cliff or by a climb into a tall tree are obvious. Yet, we still frequently hear or read about individuals accidentally (or, unfortunately, purposefully) falling from a great height to their death – rather said person was exercising good judgment or not is often disregarded. Our modern society offers many man-made high places from which to fall. Consider an individual working on the roof of a two story home when a sudden wind develops or perhaps an unaware hiker attempting to cross a rural railroad trestle finds a locomotive rushing in his direction – the height involved makes these circumstances dangerous.
Our parents and guardians warn us at a very young age of the dangers associated with getting a little too far off the ground. How many people do not suffer at least one significant fall as a child? Probably very few. This is perhaps one of the first childhood fears we must readily encounter and address. Many of us carry around the scares or other bodily irregularities that result from such a fall. These experiences may have formed painful memories that we are not eager to repeat.
A desire to want to be on the ground is natural. And one can see a fear of heights perhaps subsequently leading to a fear of boarding an especially impressive roller coaster or of flying in an aircraft from one city to another. The historical human experience has always been a grounded one and our attempts to get off the Earth’s surface for extended periods of time have occasionally garnered very tragic results.
Astraphobia (fear of lightning)
According to the National Oceanic and Atmospheric Administration, an average of 49 people has been struck and killed by lightning in the United States each year for the last three decades. Consider that the United States is one of the world’s most developed nations, where ample shelter from extreme weather is usually available. Imagine how those numbers may look for a third world nation where a large percentage of the workforce is employed outside, where weather warning systems are primitive or do not exist at all, and where ample shelter is perhaps not readily available. For every ten individuals struck by lightning, typically one will die and the other nine are generally subject to serious, and often long-term, injuries.
Aside from these statistics, lightning can be concerning or frightening in other ways. Lightning often acts as a harbinger of severe weather, including strong winds, heavy rains, and flash floods. For some, the accompanying thunder can send shivers down the spine. Early humans, given the limitations to their understanding of this atmospheric phenomenon, would have been incredibly weary of lightning.
Pyrophobia (fear of fire)
If you subscribe to the widespread, but by no means universal, belief that the Earth is 4.54 billion years old, consider that the fossil record strongly suggests that fire as we know such today did not exist on this planet until 470 million years ago. Wildfires, the great destroyers and regenerators of the wilderness (for mankind, these events are often just destroyers), were limited on Earth for another 50 million years after the first strange appearance of that now familiar flame. Fire on Earth may actually have remained somewhat of an anomaly on the planet until just six or seven million years ago. Roughly two million years ago early humans probably started using fire to cook their food and by 100,000 years ago (and perhaps as many as 1,000,000 years) fire was controlled, as much as could be expected, and used as a tool, heat source, and weapon by human beings. We can freely imagine that there was a steep learning curve involved.
Our ancestors first experiences with fire must have been terrifying, in all possible meanings of that term. Fire proved wildly significant for early man and our ability to use and control fire remains critical to all societies today. The dangers are obvious. We burn. Our belongings and homes burn. We can die from smoke inhalation if we are inside a burning building without ever seeing fire. Fire remains a dangerous, but useful, wonder.That said, there are plenty of reasons to still fear the flame.
These fears have been ingrained in the human mind since our initial appearance or arising on this planet. You might even say that these fears came programmed into our brains, regardless of our evolution or creation. Our phobias concerning these aspects of our existence may be extreme in some individuals today, but those fears have always been part of the package that is the human brain.
As early man could not have understood what was seen above the Earth in the night sky, we can understand why a fear such as cosmophobia was not included in this starter set. Of course, early man may have observed shooting stars and even encountered meteorite strikes, but these events would have been so sporadic that a legacy of danger was never connected. A few even believe that ancient man encountered extraterrestrial visitors at some early point in our collective history. Whether or not these ancient visitors from space came to spread grace or malice is moot, even the most ardent supporters of this argument must concede that these visits were infrequent or limited in scope and, apparently, stopped at some point. Thus, a fear of the cosmos above us did not need to develop. Consider too that much more of the cosmos was visible in our early history – millions upon millions of luminous dots shining down on a prehistoric Earth. The night sky was not bathed in artificial light as today and was certainly a sight to behold. In time, primitive cultures developed and the observable galaxy inspired archaic astrology and theology, but a genuine fear of the cosmos did not take root among early man.
There is research to suggest that some phobias are the product of a learned behavior, however. Our ancestors undoubtedly learned quite early that some representatives from the animal kingdom were more lethal than others. Sure, to fear a giant, hulking bear defending her young is obvious enough, but that’s because the bear is so outwardly large and ferocious. What about our smaller wild neighbors?
Consider snakes for a moment. Outwardly most snakes appear small and are afraid of humans. Snakes may even appear slow and, depending on the time of day, may appear very slow. We often stumble upon snakes, encountering these slithering creatures at times we do not expect. However, we know some snakes are very dangerous. Snakes will bite humans to defend themselves, often injecting lethal venom. This must have been traumatizing to our ancestors – that such a small and often hidden animal, perhaps one even secretly sharing our own primitive home with us, could also be deadly with just a single bite. So, when we encounter someone with ophidiophobia – a fear of snakes – today, we might imagine that there is good reason for that fear. Snakes are still potentially dangerous today and, while an excessive fear of snakes may be restrictive to some people, we can at least understand where the basis of this fear may be hardwired somewhere in the back of our minds.
That brings us to the master of all fears and the creator of a very common phobia in humans, both historically speaking and now. Achluophobia is an abnormal fear of the dark. Since time immemorial, the darkness has terrified mankind. Imagine eons ago – the darkness of the savanna on a cloudy night. A small fire is lit and the flame throws shadows in various directions into high grasses. The backs of you and your two children are pressed into an ancient tree. Just beyond the light of the fire, where the flickers of orange and yellow give way to an unfathomable black, you hear a faint giggle – almost a laugh. Then you hear this disturbing sound again, this time from another direction. These sounds are emanating from a pack of hyenas that linger just beyond the light. These nocturnal hunters can see you just fine, and, by the time you heard the first giggle, had already started to arrange themselves for an attack. Of course, you don’t know this yet. Your mind first has to race blindly down a list of explanations for the strange noises. The black darkness around you has stripped your panicked mind of mankind’s strongest sense – our vision. There is no way to know exactly what and where the danger may be and a plan of escape is equally difficult to formulate, as early man had only rudimentary means to efficiently and safely take the light along.
Thousands of years later, we take the light wherever we go throughout the night. We have lights on our cars. We have handheld lights powered by batteries. We have lights on our phones. We have invented ways to safely and easily light our houses. Still, the darkness lurks just beyond street lights in city alleys and in our yard just beyond our decorative porch lanterns.
Imagine now that there is a power outage in your town. You still intend to leave the house and attend a Christmas party perhaps twenty or thirty minutes away. The ugly sweater you had selected for the occasion is neatly folded on your dryer in the basement. Armed with a flashlight, you sally forth and down the steps into the darkness. You wiggle past a few boxes of Christmas decorations and some old lawn furniture that a careless spouse left out. You kick a box over in the darkness. As you pick up the sweater, the battery in your flashlight dies. Now engulfed in the blackness of your very own home, a giggle – a laugh really – comes from just beyond the unused boxes of Christmas décor. How sure are you that those same hyenas haven’t tracked you down across the millennia when that fire, or flashlight, has finally gone out?
The darkness we know on Earth scares us because the black of night affords cover to our other fears. We are unable to discern the unknown that lingers just beyond the light and our imaginations pack all of our fears into that spot at once. In many ways, being afraid of the dark was both prescribed to early man and learned as time passed. Historic nighttime dangers have been eliminated or tamed. For example, most of us may exit our homes at night and head for the local tavern without fearing an attack from a pack of wolves. However, new threats in the darkness have emerged. As we approach that tavern, we may become panicked if several shouts and a gunshot ring out from a dark alley. Being afraid of the dark is natural for this reason, and perhaps even celebrated in our culture. We have even learned to enjoy the entertainment value of the sensations associated with this fear. Of course, despite our best efforts, the darkness of Earth has never fully been eliminated or tamed. Our lights have only done so much. Perhaps some of us dread the darkness more than others – for some this fear has become a true phobia – only because the dark can mask our other phobias.
For instance, when reading about the scenario of the flashlight dying in the basement, if you imagined the dark recesses of those boxes and lawn chairs concealing a murderous clown snickering at you, then you may have coulrophobia – a fear of clowns. Coulrophobia is one of the new phobias that has developed fairly recently in our society. This list of new phobias is incredibly extensive. Obviously, early humans scratching out a life in prehistory had no concept of coulrophobia. Those early humans could not have known ecclesiophobia, a fear of churches; globophobia, a fear of balloons; or siderodromophobia, a fear of the railroad either. These particulars were not yet known – did not exist – millennia ago. Unless you subscribe to the ancient astronaut version of human history, then early man could not have had mechanophia – the fear of machines. Surely, one of the most modern (and, arguably, man-made) phobias must be hexakosioihexekontahexaphobia – the fear of the number 666. These fears did not exist long ago because such fears simply could not – the subject of those fears were unknown to even the most imaginative of our early ancestors.
This brings us back to cosmophobia. Cosmophobia is the new achluophobia. The vast darkness of the cosmos hides all our newfound worries and concerns about our survival and existence. Our most powerful lenses can only see so far into the cosmos and have always presented us with more questions – more unknowns – than answers. Our probes and machines can only tell us so much before their intricate pieces and gears disappear in the immeasurable space that has always encircled Earth. We have largely mastered our world, and in doing so we’ve suffered some missteps and learned what to fear along the way. Much of what was unknown in the darkness of our world historically speaking is now an afterthought. So, what is the cosmos hiding from us in all that darkness? We look up and wonder.
Considerable knowledge has been gained about our solar system, our intimate corner of the cosmos, just in the last four centuries. Are there any massive asteroids heading our way? What about deadly radiation that seems to seep out of everything in space? When will the sun betray and destroy us? Where the hell are those little green men we were so sure existed? And, should something happen to the only rock we’ve ever known, is there another place in space we can go? We want to know. Our wait for this knowledge will not be a long one.
Soon, we’ll be dragging our fires – our lights – and our couple millennia worth of fears up there to find out. This journey will not be for the cosmophobes among us. In fact, maybe the cosmophobes, no matter how irrational, will proudly announce one day that they were correct and justified in their fear of the universe and all the secrets shrouded above us at night. There’s no doubt that on these early journeys in the cosmos, we will be right back against that tree with a small fire dying in front of us. We will imagine all of our fears waiting for us on the other side. Dying Up There illuminates one possibility waiting in that dark space just beyond the light of man.
So, is there a good reason to be afraid of space? Will cosmophobia ever unseat some of mankind’s more common fears?
There are a handful of moons in our solar system that may be an abode for extraterrestrial life. After comparison, which of the candidates makes the strongest case?
During the course of my career as an educator, I’ve tried to create a wide variety of opportunities for my students to earn extra credit. Some of these activities have undoubtedly been more popular than others, and a few were especially well received.
About two years ago, I came up with a relatively simple task for my students to perform over a weekend near the end of the school year. Any student successfully completing the optional assignment by the following Monday would receive a handful of bonus points for that grading period.
I put this list of traditionally female names on my chalkboard:
Students were permitted to copy the list. Along with the list, students were posed with this question to answer:
What is this a list of?
Throughout the course of the day, which included six classes, a few students wanted to offer a guess or two right away. Feeling confident that no student would immediately know the answer, I allowed for a few guesses to be taken at the end of each class.
“A list of Disney characters?”
This guess was actually made several times throughout the day. Although not the answer I was looking for, I do understand why that assumption would be put forth given the first name on the list.
“A list of women you’ve dated?”
To this colorful response (which I am sure was made largely in jest), I offered back only that “I’ve actually never dated a Juliet.”
Several students in each class did submit a correct answer by the following Monday. This list is, of course, of moons (natural satellites) in our solar system. Most of the students submitting correct responses had found the answer in the way I assumed the majority would: an online search engine. However, at least one student insisted that a video game had provided him with enough information to take an educated guess. Finding out how and where the students sought an answer to my question was definitely interesting to me.
Many students were surprised to learn that our solar system includes nearly two hundred moons or “natural satellites”, including our own Moon – which is one of the largest.
I’ve recently been researching some of the moons in our solar system to a considerable extent. My goal had been to decide which would serve me best as one of the settings of a science fiction piece I’m hoping to complete this summer – Dying Up There. The only real requirement for selection was that the moon be a realistic candidate to host life (and, in this case, specifically aquatic life). This is not a complete list of all the candidates, but these three really seemed to make strong cases to me: Europa, Enceladus, and Titan. Each of these moons appear to possess considerable quantities of liquid. There are good arguments supporting the belief that the bodies of liquid on each moon may be suitable for extraterrestrial life.
Europa is a moon of Jupiter, whereas Enceladus and Titan both orbit Saturn.
Prior to my research, my mind went immediately to Europa. Europa has been a standby in the world of science fiction, especially over the last four decades, as a potential home to extraterrestrial life. However, my research nearly convinced me to stray elsewhere.
Comparable to our moon in size, Europa is probably best known for being featured prominently in the 1984 film 2010: The Year We Make Contact and the novel on which the film is based. More recent films, such as Europa Report, have kept the moon in the popular imagination. Europa is a favorite of science fiction writers (and of NASA) for good reason: there is strong evidence to support that this moon is home to an ocean 60 miles deep. By comparison, the deepest part of the Earth’s ocean is not quite seven miles from surface to bottom.
A quick look at an image of Europa will not reveal this massive ocean. Europa is, at any given time, five times farther away from the Sun than Earth. Europa’s surface is also far colder than any spot on Earth, even the most frigid regions of Antarctica. As a result, Europa’s ocean is believed to be frozen upwards of 20 miles deep. Thanks to tidal heating, a considerable part of this ocean may remain liquid. If hydrothermal vents on the seafloor are functional, as some strongly believe, this may allow for life forms to exist using chemosynthesis in a body of water with a chemical composition similar to our oceans. There is a minority view that this ice-covered ocean may even occasionally melt through to the surface, producing what is referred to as “chaos terrain”. If this theory holds true, there may be a handful of locations on Europa’s smooth surface where the ocean is just “tens of meters” below the ice. Moreover, NASA has recently suggested that some features on Europa’s surface are covered in sea salt.
There are some regrettable drawbacks of Europa serving as a setting within my current work. The first being that Europa’s familiarity through many other appearances in science fiction over the last few decades boils away some of the “unknown” quality the moon may have previously possessed. Europa has essentially become the Mars of our generation, in terms of where science fiction writers suggest some kind of advanced extraterrestrial life may be encountered. There is also the pesky fact that Europa is bathed in radiation from Jupiter, making future human exploration there especially problematic.
Also worth mention is the fact that at least a few in the scientific community suspect that Europa’s ocean is biologically dead. Despite these less optimistic feelings, NASA has proposed a wide array of exploratory missions for Europa.
Enceladus could very well be what everyone wants Europa to be: a bastion of life in our solar system beyond the Earth. This tiny moon of Saturn is very remote, nearly ten times farther away from the Sun than the Earth, and has been only a bit player in the world of science fiction since first being discovered in 1789. Take a good look at the picture to the left. Doesn’t Enceladus look like a snowball? Oddly enough, cryovolcanoes on this little moon blast water vapor into space. As a result, some of this vapor falls back to the surface as what might be described as snow.
These cryovolcanoes are largely found in the southern region of the moon, and researchers believe that an ocean exists there beneath an ice shell. This is not a Europa-sized ocean, as Enceladus is only believed to be home to an ocean comparable to some of the larger bodies of water on Earth. However, this smaller Enceladus ocean is also believed to have a generally thinner ice covering than the oceans on Europa. Recent studies suggest that the ice covering this southern ocean on Enceladus is just three miles thick. Compare that to Europa’s expected average ice thickness and the ocean on Enceladus becomes immediately easier to access and explore.
An ocean on Enceladus could be kept liquid under a layer of ice by the same processes that may be working for Europa. Tidal heating is believed to trigger considerable geological activity on this moon, creating an array of fractures across the surface. This is conducive to keeping at least some of this ocean as liquid and helps create the unique chemical mix believed to exist within that sea. There is strong evidence that suggests hydrothermal activity may be at work below the ice and that the core of Enceladus allows water to freely enter through fissures and cracks to pick up additional heat.
However, Enceladus is not necessarily ideal for the setting I need. The conditions on Enceladus are not as grand as on Europa and the sheer number of possibilities seem somewhat limited compared to the latter. More troubling is a new study that states Enceladus is only one hundred million years old. That may seem ancient, but in the grand scheme of existence that is a relatively quick tick of the clock. Most sources suggest that life on Earth took almost one billion years to emerge. Enceladus may be painfully young on a cosmic scale and any life developing in that moon’s ocean must assuredly be very primitive.
Titan, no stranger to the world of science fiction, is Saturn’s largest moon and brings an entirely different set of attributes to the table. Larger than Europa and Enceladus, Titan is the second largest moon in the solar system. Aside from the Earth, Titan is also the only other body in the solar system with surface liquid. Titan is shrouded in a thick atmosphere and only in the last two decades have researchers gained a good understanding of this moon’s surface. Unlike nearby Enceladus, Titan is believed to be ancient. However, Titan’s surface is fairly young, which suggests recent geological activity. Titan is oddly Earth-like: there is precipitation, eroded channels cutting across the surface, and large bodies of liquid present.
Of course, Titan is very, very cold. This is not liquid water collecting on the surface of Titan, but liquid methane. Possessing a much lower freezing point, methane is able to exist as a liquid on Titan (also possessing a much lower boiling point, methane appears as a gas on Earth). Enough liquid methane rains down on the surface that substantial lakes and seas have formed in a few locations on Titan. Several of these bodies of liquid have been named. The largest three are Kraken Mare, Ligeia Mare, and Punga Mare. Kraken Mare is the most impressive at over 500 feet deep and covering an area larger than Earth’s Caspian Sea. The largest bodies of liquid methane on Titan are found near the poles, where the indirect sunlight struggles to evaporate these seas.
Titan may also have liquid water under the surface, but most studies regarding such a ocean have taken a backseat to the lakes and seas on the surface. Life on Titan would be seriously hindered by the extreme cold and the moon’s atmosphere offers many additional complications.
If Titan is without life now, the future may be somewhat brighter. Literally. When the sun becomes a red giant, Titan may warm up enough to become much more hospitable to life. Unfortunately, these conditions would not last forever. The Earth would also be destroyed or jettisoned from the solar system by the same changes in the Sun. So, I don’t think too many people are looking forward to Titan’s potentially improved conditions.
Also worthy of note is that in 2005 a spacecraft from Earth landed on Titan, making the latter the most distant body landed on by a craft from the former.
Titan is incredibly interesting and really seems to have a very unique existence within our solar system. However, Titan is almost too far from where my imagination initially started. Titan’s methane lakes are undoubtedly science fiction worthy, but I really needed a definitely ice-covered sea to serve as a setting within Dying Up There.
Tentatively, I am going with Europa. Europa may not as edgy as Enceladus, but the wonder and possibilities associated with the former have created a legacy of intrigue. Enceladus makes for a solid backup plan. The very thought of jumping (or falling) into an alien sea, regardless of the temperature, is incredibly unnerving to me and that’s exactly the type of feeling I’m looking to create in my future readers.
Outside the realm of storytelling though, any of these moons make interesting candidates to host life and are worthy of exploration. This is, of course, a limited list. Which of these three seems the most likely to actually host life? Are there any other moons in our solar system worth throwing into the debate for best place to find extraterrestrial life in our solar system?